# Chapter 10: Projectile And Satellite Motion

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• 1.

### According to Kepler's laws, the paths of planets about the sun are

• A.

Parabolas.

• B.

Circles.

• C.

Straight lines.

• D.

Ellipses.

• E.

None of these

D. Ellipses.
Explanation
According to Kepler's laws, the paths of planets about the sun are ellipses. Kepler's first law, also known as the law of orbits, states that planets move in elliptical orbits with the sun at one of the focal points. This means that the path of a planet is not a circle, parabola, or a straight line, but rather an ellipse. Therefore, the correct answer is ellipses.

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• 2.

### Both Newton and Kepler considered forces on the planets. Kepler hypothesized the direction of the forces was

• A.

Along their directions of travel.

• B.

Toward the sun.

• C.

neither

A. Along their directions of travel.
Explanation
Both Newton and Kepler considered forces on the planets. Kepler hypothesized that the direction of the forces acting on the planets was along their directions of travel. This means that the force exerted on a planet would be in the same direction as its motion. Kepler's hypothesis was based on his observations of the planets' orbits and his belief that there must be a force causing them to move in a curved path. This hypothesis was later proven incorrect by Newton, who proposed that the force acting on the planets was actually directed toward the sun.

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• 3.

### Which of the following is not a vector quantity?

• A.

Velocity

• B.

Speed

• C.

Acceleration

• D.

None are vector quantities.

• E.

All are vector quantities.

B. Speed
Explanation
Speed is not a vector quantity because it only has magnitude and does not have a specific direction. Velocity and acceleration, on the other hand, are vector quantities as they have both magnitude and direction. Therefore, the correct answer is speed.

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• 4.

### An airplane that flies at 100 km/h in a 100 km/h hurricane crosswind has a ground speed of

• A.

0 km/h.

• B.

100 km/h.

• C.

141 km/h.

• D.

200 km/h.

C. 141 km/h.
Explanation
When an airplane is flying in a crosswind, the wind affects its ground speed. In this scenario, the airplane is flying at 100 km/h, and there is a 100 km/h hurricane crosswind. The crosswind will not affect the airplane's speed directly, but it will cause the airplane to drift sideways. The airplane's ground speed is the vector sum of its airspeed and the crosswind. Since the crosswind is equal to the airplane's airspeed, the ground speed will be the square root of the sum of the squares of the airspeed and crosswind. Using the Pythagorean theorem, the ground speed is calculated to be approximately 141 km/h.

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• 5.

### An airplane travels at 141 km/h toward the northeast. What is its component of velocity due north?

• A.

41 km/h

• B.

100 km/h

• C.

110 km/h

• D.

141 km/h

B. 100 km/h
Explanation
The airplane is traveling towards the northeast, which is a diagonal direction. To find the component of velocity due north, we need to consider the northward direction. Since the northeast direction is at a 45-degree angle with the north, we can use trigonometry to find the northward component of velocity. The northward component is equal to the velocity multiplied by the cosine of the angle. In this case, the northward component is 141 km/h multiplied by the cosine of 45 degrees, which is approximately 100 km/h.

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• 6.

### A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its vertical component of velocity

• A.

Increases.

• B.

Remains unchanged.

• C.

Decreases.

C. Decreases.
Explanation
When a rock is thrown upward at an angle of 50 degrees with respect to the horizontal, its initial velocity is divided into two components - horizontal and vertical. The vertical component of velocity determines the rock's upward or downward motion. As the rock rises, the force of gravity acts against its upward motion, causing its vertical velocity to decrease. Therefore, the correct answer is that the vertical component of velocity decreases.

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• 7.

### A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity

• A.

Increases.

• B.

Remains unchanged.

• C.

Decreases.

B. Remains unchanged.
Explanation
When a rock is thrown upward at an angle of 50 degrees with respect to the horizontal, the only force acting on it is gravity. Gravity only affects the vertical component of velocity, causing the rock to slow down as it rises and speed up as it falls. However, the horizontal component of velocity is not affected by gravity. Therefore, neglecting air drag, the horizontal component of velocity remains unchanged throughout the motion of the rock.

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• 8.

### A stone is thrown horizontally from the top of a cliff. One second after it has left your hand, its vertical distance below the top of the cliff is

• A.

5 m.

• B.

10 m.

• C.

15 m.

A. 5 m.
Explanation
When a stone is thrown horizontally, its initial vertical velocity is zero. Therefore, the stone only experiences the force of gravity acting vertically downwards. In one second, the stone will fall a distance of 5 meters due to the acceleration of gravity (9.8 m/s^2) acting on it. Thus, its vertical distance below the top of the cliff after one second is 5 meters.

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• 9.

### Throw an object upward at a 45 degree angle. With no gravity it will follow a straight-line path. But because of gravity, at the end of 1 second, it is

• A.

About 5 m below the straight line.

• B.

About 10 m below the straight line.

• C.

About 15 m below the straight line.

A. About 5 m below the straight line.
Explanation
When an object is thrown upward at a 45-degree angle, it experiences the force of gravity pulling it downward. This force causes the object to deviate from its straight-line path. After 1 second, the object will have fallen a certain distance below the straight line due to gravity. Since the question states that the object is about 5 m below the straight line after 1 second, this suggests that gravity has caused the object to fall downward during that time period.

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• 10.

### Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity

• A.

Decreases.

• B.

Remains constant.

• C.

Increases.

B. Remains constant.
Explanation
When a bowling ball is rolled off the edge of a table, it experiences only vertical acceleration due to gravity, while its horizontal velocity remains unchanged. This is because there are no horizontal forces acting on the ball, such as air resistance or a push. Therefore, the horizontal component of velocity remains constant throughout the fall.

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• 11.

### A bullet fired horizontally from a rifle begins to fall

• A.

As soon as it leaves the barrel.

• B.

After air friction reduces its speed.

• C.

Neither of these

A. As soon as it leaves the barrel.
Explanation
When a bullet is fired horizontally from a rifle, it already has an initial vertical velocity component due to the force of gravity acting on it. As a result, it begins to fall as soon as it leaves the barrel, regardless of whether air friction affects its speed or not. This is because the force of gravity constantly pulls the bullet downwards, causing it to follow a curved trajectory.

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• 12.

### A projectile is launched vertically upward at 50 m/s. If air resistance is negligible, its speed upon returning to its starting point is

• A.

Less than 50 m/s.

• B.

50 m/s.

• C.

More than 50 m/s.

B. 50 m/s.
Explanation
When a projectile is launched vertically upward, it experiences a constant acceleration due to gravity, causing it to slow down until it reaches its highest point. At this point, its velocity becomes zero, and it starts to fall back down. As there is no air resistance, the projectile will regain its initial velocity of 50 m/s when it returns to its starting point. Therefore, the speed upon returning to its starting point is 50 m/s.

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• 13.

### An Earth satellite is simply a projectile

• A.

Freely falling around the Earth.

• B.

Floating motionless in space near the Earth.

• C.

Approaching the Earth from outer space.

A. Freely falling around the Earth.
Explanation
An Earth satellite is considered to be freely falling around the Earth because it is constantly under the influence of Earth's gravitational pull. The satellite is in a state of continuous free fall, where the gravitational force is balanced by its forward motion, resulting in a stable orbit around the Earth. This allows the satellite to remain in space without any propulsion or external forces.

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• 14.

### Earth satellites are typically more than 100 km high so as to be above the Earth's

• A.

Atmosphere.

• B.

Gravitational field.

• C.

Both of these

A. AtmospHere.
Explanation
Earth satellites are typically more than 100 km high to be above the Earth's atmosphere. This is because the atmosphere can interfere with satellite signals and cause disruptions in communication and data transmission. By placing satellites above the atmosphere, they can operate more efficiently and effectively without any interference. Additionally, being above the atmosphere also allows satellites to have a better view of Earth's surface for various purposes such as weather monitoring, navigation, and remote sensing.

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• 15.

### A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of velocity because

• A.

It is not acted on by any forces.

• B.

It is not acted on by any horizontal forces.

• C.

It has no vertical component of velocity to begin with.

• D.

The net force acting on it is zero.

• E.

None of these

B. It is not acted on by any horizontal forces.
Explanation
The correct answer is "it is not acted on by any horizontal forces." This is because in the absence of air resistance, there are no external forces acting horizontally on the projectile. Therefore, the projectile will continue to move horizontally with a constant velocity. The other options are incorrect because they do not fully explain why the projectile maintains its horizontal component of velocity.

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• 16.

### A hunter on level ground fires a bullet at an angle of 10 degrees above the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?

• A.

The dropped one

• B.

The fired one

• C.

Both hit at the same time.

A. The dropped one
Explanation
The dropped bullet will hit the ground first because it is not affected by the horizontal component of its velocity. The fired bullet, on the other hand, has both a horizontal and vertical component of velocity. Even though the fired bullet is initially moving faster due to the force of the rifle, it will take longer to reach the ground because it also has to cover horizontal distance before hitting the ground. Therefore, the dropped bullet will hit the ground first.

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• 17.

### A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?

• A.

The dropped one

• B.

The fired one

• C.

Both hit at the same time.

B. The fired one
Explanation
The bullet that is fired at an angle of 2 degrees below the horizontal will hit the ground first. This is because the horizontal component of its velocity will contribute to its forward motion, while the vertical component will contribute to its downward motion. On the other hand, the bullet that is dropped from the level of the rifle will only be affected by gravity pulling it straight down. Therefore, the fired bullet will reach the ground before the dropped bullet.

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• 18.

### A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in

• A.

Less than 0.5 s.

• B.

More than 0.5 s.

• C.

0.5 s.

C. 0.5 s.
Explanation
If a bullet is fired horizontally over level ground, it will have a constant horizontal velocity. This means that the time it takes for the bullet to hit the ground is solely determined by the vertical motion. The vertical motion is influenced by the force of gravity, which causes the bullet to accelerate downward. Since the bullet is fired horizontally, the initial vertical velocity is zero. Therefore, the time it takes for the bullet to hit the ground is the same regardless of its initial speed. This is why the bullet would still hit the ground in 0.5 seconds even if it had been fired with twice the speed.

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• 19.

### An object is dropped and freely falls to the ground with an acceleration of 1 g. If it is thrown upward at an angle instead, its acceleration will be

• A.

0 g.

• B.

1 g downward.

• C.

1 g upward.

• D.

Larger than 1 g.

• E.

None of these

B. 1 g downward.
Explanation
When an object is dropped and freely falls to the ground, its acceleration is equal to the acceleration due to gravity, which is approximately 9.8 m/s^2 or 1 g. When the object is thrown upward at an angle, it still experiences the acceleration due to gravity acting downward. This is because gravity always acts vertically downward regardless of the object's motion. Therefore, the acceleration of the object when thrown upward at an angle will still be 1 g, but in the downward direction.

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• 20.

### A projectile is launched at ground level an angle of 15 degrees above the horizontal and lands down range. What other projection angle for the same speed would produce the same down-range distance?

• A.

30 degrees

• B.

45 degrees

• C.

50 degrees

• D.

75 degrees

• E.

90 degrees

D. 75 degrees
Explanation
If a projectile is launched at an angle of 15 degrees above the horizontal and lands down range, another projection angle of 75 degrees would produce the same down-range distance. This is because the range of a projectile depends on the horizontal component of its velocity. The maximum range is achieved when the projectile is launched at a 45-degree angle. As the angle increases beyond 45 degrees, the range decreases. Therefore, if the initial angle is 15 degrees, the same down-range distance can be achieved by increasing the angle to 75 degrees.

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• 21.

### A projectile is fired into the air at an angle of 50 degrees with the ground and lands on a target that is at the same level at which the projectile started. It will also land on the target if it is fired at an angle of

• A.

40 degrees.

• B.

45 degrees.

• C.

55 degrees.

• D.

60 degrees.

• E.

None of these

A. 40 degrees.
Explanation
When a projectile is fired into the air at an angle of 50 degrees, it follows a curved path known as a parabola. The range of the projectile is determined by the initial velocity and the angle of projection. Since the target is at the same level as the projectile's starting point, the range remains the same. In order for the projectile to land on the target, it must have the same range. Among the given options, firing the projectile at an angle of 40 degrees will result in the same range, allowing it to land on the target.

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• 22.

### A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 second later?

• A.

50 m

• B.

98

• C.

100

• D.

490

C. 100
Explanation
The bullet will be 100 meters downrange after 1 second because the horizontal velocity of the bullet remains constant throughout its trajectory. Therefore, in 1 second, the bullet will travel 100 meters horizontally.

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• 23.

### Two projectiles are fired from ground level at equal speeds but different angles. One is fired at an angle of 30 degrees and the other at 60 degrees. The projectile to hit the ground first will be the one fired at (neglect air resistance)

• A.

30 degrees.

• B.

60 degrees.

• C.

Both hit at the same time.

A. 30 degrees.
Explanation
The projectile fired at 30 degrees will hit the ground first because it has a smaller angle of launch, which means it has a greater horizontal component of velocity. The horizontal component of velocity determines how fast the projectile moves horizontally, while the vertical component determines how high the projectile goes. Since both projectiles are fired at the same speed, the one with a smaller angle will have a greater horizontal velocity and therefore reach the ground first.

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• 24.

### After a rock thrown straight up reaches the top of its path and then falls a short distance, its acceleration is (neglect air resistance)

• A.

Greater than when it was at the top of its path.

• B.

Less than when it was at the top of its path.

• C.

The same as it was at the top of its path.

C. The same as it was at the top of its path.
Explanation
When the rock reaches the top of its path, its velocity becomes zero, but its acceleration remains the same. This is because acceleration is the rate of change of velocity, and even though the velocity is momentarily zero, the acceleration is still acting on the rock due to the force of gravity. As the rock falls a short distance from the top, its acceleration continues to be the same, as there is no change in the force acting on it. Therefore, the acceleration of the rock is the same as it was at the top of its path.

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• 25.

### A projectile is fired vertically from the surface of the Earth at 8 km/s. The projectile will

• A.

Go into circular orbit about the Earth.

• B.

Rise and fall back to the Earth's surface.

• C.

Follow an uncertain path.

• D.

Escape from the Earth.

B. Rise and fall back to the Earth's surface.
Explanation
The projectile will rise and fall back to the Earth's surface because its initial velocity is not sufficient to achieve escape velocity from Earth's gravitational pull. Therefore, it will follow a parabolic trajectory and eventually return to the surface.

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• 26.

### The ground speed of an airplane that has an airspeed of 200 km/h when it is in a 200-km/h crosswind is

• A.

0 km/h.

• B.

200 km/h.

• C.

283 km/h.

• D.

400 km/h.

• E.

1600 km/h.

C. 283 km/h.
Explanation
When an airplane is flying in a crosswind, the ground speed is the combination of the airplane's airspeed and the speed of the crosswind. In this case, the airspeed of the airplane is 200 km/h, and the crosswind is also 200 km/h. To find the ground speed, we can use the Pythagorean theorem to calculate the resultant velocity. The formula is V^2 = A^2 + B^2, where V is the resultant velocity, and A and B are the two perpendicular components (airspeed and crosswind). Plugging in the values, we get V^2 = 200^2 + 200^2. Solving this equation gives us V = 283 km/h, which is the ground speed of the airplane.

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• 27.

### Without air resistance, a projectile fired horizontally at 8 km/s from atop a mountain would

• A.

Accelerate downward at g as it moves horizontally.

• B.

Trace a curve that matches the earth's curvature.

• C.

Return later to its starting position and repeat its falling behavior.

• D.

All of these

• E.

None of these

D. All of these
Explanation
When a projectile is fired horizontally with a high initial velocity, it will continue to move horizontally at a constant speed due to the absence of air resistance. However, it will also accelerate downward at a rate equal to the acceleration due to gravity (g). This means that as the projectile moves horizontally, it will also fall vertically, following a curved path that matches the curvature of the Earth. Eventually, if the mountain is tall enough and the initial velocity is high enough, the projectile will return to its starting position and repeat its falling behavior. Therefore, all of the given options are correct explanations for the behavior of the projectile.

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• 28.

### An object is thrown vertically into the air. Because of air resistance, the time for its descent will be

• A.

Longer than the ascent time.

• B.

Shorter than the ascent time.

• C.

Equal to the ascent time.

• D.

Not enough information given to say.

A. Longer than the ascent time.
Explanation
When an object is thrown vertically into the air, it experiences the force of gravity pulling it downwards and air resistance acting against its upward motion. The force of air resistance slows down the object's descent, making it take longer to reach the ground compared to the time it took to ascend. Therefore, the time for the object's descent will be longer than the ascent time.

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• 29.

### A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The player sees the ball land 20 m down range. What is the player's pitching speed?

• A.

• B.

• C.

• D.

• E.

None of these

C. About 20 m/s
Explanation
The player's pitching speed can be determined using the horizontal motion equation, which states that the horizontal distance traveled by an object is equal to its horizontal velocity multiplied by the time of flight. In this case, the ball was thrown horizontally, so its initial vertical velocity is zero. Therefore, the time of flight can be calculated using the vertical motion equation, which states that the final vertical position is equal to the initial vertical position plus the initial vertical velocity multiplied by the time of flight, plus half the acceleration due to gravity multiplied by the square of the time of flight. Solving for time of flight, we find that it is equal to the square root of twice the initial vertical position divided by the acceleration due to gravity. Plugging in the values, we find that the time of flight is approximately 0.71 seconds. Using the horizontal motion equation and plugging in the values for the horizontal distance traveled and the time of flight, we can solve for the horizontal velocity, which is the player's pitching speed. The calculated value is approximately 20 m/s.

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• 30.

### An airplane flies at 40 m/s at an altitude of 50 meters. The pilot drops a heavy package which falls to the ground. Where, approximately, does the package land relative to the plane's new position?

• A.

Beneath the plane

• B.

400 m behind the plane

• C.

500 m behind the plane

• D.

More than 500 m behind the plane

• E.

None of these

A. Beneath the plane
Explanation
The package will land beneath the plane because when an object is dropped from a moving airplane, it will continue to move horizontally with the same velocity as the plane. However, it will accelerate vertically due to gravity. As a result, the package will fall straight down relative to the plane's new position, landing beneath it.

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• 31.

### A bullet is fired horizontally with an initial velocity of 300 m/s from a tower 20 m high. If air resistance is negligible, the horizontal distance the bullet travels before hitting the ground is about

• A.

200 m.

• B.

300 m.

• C.

400 m.

• D.

500 m.

• E.

600 m.

E. 600 m.
Explanation
When a bullet is fired horizontally, it only has an initial horizontal velocity and no vertical velocity. Therefore, it will continue to travel horizontally until it hits the ground. The time it takes for the bullet to hit the ground can be calculated using the equation: time = square root of (2 * height / g), where g is the acceleration due to gravity. Substituting the given values, we find that the time is approximately 2 seconds. Since the bullet is traveling horizontally at a velocity of 300 m/s for 2 seconds, the horizontal distance it travels is 300 m/s * 2 s = 600 m.

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• 32.

### A river 100 m wide flows due south at 1 m/s. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat reaches the east bank

• A.

Due east of where it started.

• B.

141 m farther south than where it started.

• C.

100 m farther south than where it started.

• D.

100 m farther north than where it started.

C. 100 m farther south than where it started.
Explanation
The boat is crossing the river at a speed of 1 m/s due east, while the river is flowing south at a speed of 1 m/s. This means that the boat is effectively moving at a diagonal speed of âˆš(1^2 + 1^2) = âˆš2 m/s. Since the river is 100 m wide, it will take the boat 100/âˆš2 â‰ˆ 70.71 seconds to cross the river. During this time, the boat will also be carried south by the river's current at a speed of 1 m/s. Therefore, the boat will end up 70.71 m farther south than where it started, resulting in the correct answer of 100 m farther south than where it started.

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• 33.

### A river 100 m wide flows due south. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. Relative to the Earth, the boat travels

• A.

Nowhere.

• B.

141 m.

• C.

100 m.

• D.

200 m.

• E.

241 m.

B. 141 m.
Explanation
The boat is pointed due east and crosses the river, which is flowing due south. This means that the boat is moving perpendicular to the current of the river. As a result, the boat's eastward motion is canceled out by the southward motion of the river, and the boat ends up moving neither north nor south. Therefore, the boat travels nowhere in terms of its north-south position. However, the boat does travel 100 meters across the river due to its eastward motion. Additionally, the boat takes 100 seconds to cross the river, since it is traveling at a rate of 1 m/s and the river is 100 meters wide. Therefore, the boat's overall displacement is the hypotenuse of a right triangle with legs of 100 meters and 100 seconds, which is approximately 141 meters.

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• 34.

### A river 100 m wide flows due south. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat crosses in

• A.

50 s.

• B.

100 s.

• C.

141 s.

• D.

200 s.

B. 100 s.
Explanation
The boat is moving eastward at a speed of 1 m/s relative to the water. Since the river is flowing southward, the boat's actual velocity will be the vector sum of its eastward velocity and the river's southward velocity. The boat needs to travel a distance of 100 m to cross the river. Therefore, the time taken to cross the river can be calculated by dividing the distance by the boat's actual velocity. In this case, 100 m divided by 1 m/s equals 100 s.

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• 35.

### A river 100 m wide flows due south at 1 m/s. A boat that goes 1 m/s relative to the water leaves the west bank. To land at a point due east of its starting point, the boat must be pointed

• A.

Northeast.

• B.

East.

• C.

Southeast.

• D.

Nowhereâ€”it can't be done.

D. Nowhereâ€”it can't be done.
Explanation
The boat needs to travel directly east to land at a point due east of its starting point. However, the river is flowing due south, which means that the boat will be carried downstream while trying to travel east. Since the boat can only move at a speed of 1 m/s relative to the water, it will not be able to counteract the river's flow and reach its desired destination. Therefore, the boat cannot be pointed in any direction to successfully land due east.

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• 36.

### The tangential velocity of an Earth satellite is its velocity

• A.

Parallel to the surface of the Earth.

• B.

Perpendicular to the surface of the Earth.

• C.

Attributed to satellites moving in any direction.

A. Parallel to the surface of the Earth.
Explanation
The tangential velocity of an Earth satellite is its velocity parallel to the surface of the Earth because satellites in orbit around the Earth move in a circular or elliptical path. This means that their velocity is always perpendicular to the radius of their orbit, which is directed towards the center of the Earth. Since the radius is perpendicular to the surface of the Earth, the tangential velocity must be parallel to the surface.

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• 37.

### The radial velocity of an Earth satellite is its velocity

• A.

Parallel to the surface of the Earth.

• B.

Perpendicular to the surface of the Earth.

• C.

Attributed to satellites moving in any direction.

• D.

None of these

B. Perpendicular to the surface of the Earth.
Explanation
The radial velocity of an Earth satellite refers to its velocity perpendicular to the surface of the Earth. This means that it is the component of the satellite's velocity that is directed towards or away from the center of the Earth. The other options are incorrect because they do not accurately describe the direction of the satellite's velocity.

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• 38.

### If a satellite's radial velocity is zero at all times, its orbit must be

• A.

Parabolic.

• B.

Elliptical.

• C.

Circular.

• D.

Geosynchronous.

C. Circular.
Explanation
If a satellite's radial velocity is zero at all times, it means that its distance from the center of the orbit remains constant. This can only happen in a circular orbit, where the gravitational force acting on the satellite is balanced by its centripetal force. In a parabolic or elliptical orbit, the satellite's distance from the center would vary, resulting in a non-zero radial velocity. Geosynchronous orbit refers to a specific type of circular orbit where the satellite's period of rotation matches the Earth's rotation, but it does not necessarily imply zero radial velocity.

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• 39.

### Planets would crash into the sun if it weren't for

• A.

Their tangential velocities.

• B.

Their vast distances from the sun.

• C.

The inverse-square law.

• D.

Their relatively small masses.

• E.

The fact that they are beyond the main gravitation of the sun.

A. Their tangential velocities.
Explanation
The tangential velocities of the planets prevent them from crashing into the sun. This is because the planets are moving in a circular orbit around the sun, and the tangential velocity provides the necessary centrifugal force to balance the gravitational force between the planet and the sun. Without the tangential velocities, the planets would be pulled directly towards the sun and collide with it.

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• 40.

### What prevents satellites such as the space shuttle from falling?

• A.

Gravity

• B.

Centripetal force

• C.

Centrifugal force

• D.

The absence of air drag

• E.

Nothing; they are continually falling as they orbit the Earth.

E. Nothing; they are continually falling as they orbit the Earth.
Explanation
Satellites such as the space shuttle do not fall to the Earth because they are in a state of constant freefall as they orbit the Earth. This is due to the balance between their forward motion and the gravitational pull of the Earth. Although gravity is present and constantly pulling the satellite towards the Earth, the satellite's forward motion keeps it in orbit, resulting in a continuous falling motion. Therefore, the correct answer is that nothing prevents satellites from falling as they orbit the Earth.

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• 41.

### The circular path of a satellite orbiting the Earth is characterized by a constant

• A.

Speed.

• B.

Acceleration.

• C.

• D.

All of these

• E.

None of these

D. All of these
Explanation
The circular path of a satellite orbiting the Earth is characterized by a constant speed because the satellite maintains a consistent velocity as it travels around the Earth. Additionally, the satellite experiences acceleration because it is constantly changing direction as it orbits. Lastly, the radial distance remains constant as the satellite orbits, as it maintains a fixed distance from the center of the Earth. Therefore, all of these options accurately describe the characteristics of a satellite's circular orbit.

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• 42.

### An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is

• A.

Nearest the Earth.

• B.

Farthest from the Earth.

• C.

It travels at constant speed everywhere in orbit.

A. Nearest the Earth.
Explanation
An Earth satellite in an elliptical orbit experiences varying distances from the Earth. According to Kepler's laws of planetary motion, a satellite moves faster when it is closer to the body it orbits. Therefore, when the satellite is nearest to the Earth in its elliptical orbit, it travels at its fastest speed.

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• 43.

### The fastest moving planet in a solar system is

• A.

The smallest planet.

• B.

The most massive planet.

• C.

The planet nearest the sun.

• D.

The planet farthest from the sun.

• E.

Any planet, for they all move at the same speed.

C. The planet nearest the sun.
Explanation
The correct answer is the planet nearest the sun. This is because the closer a planet is to the sun, the stronger the gravitational pull it experiences. This gravitational pull causes the planet to move faster in its orbit around the sun. Therefore, the planet nearest the sun will have the highest orbital speed and will be the fastest moving planet in the solar system.

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• 44.

### It takes Pluto a longer time to orbit the sun than the Earth does because Pluto

• A.

Has much further to go.

• B.

Goes much slower.

• C.

Choices A and B are both correct.

• D.

None of the above

C. Choices A and B are both correct.
Explanation
Pluto takes a longer time to orbit the sun than the Earth because it has much further to go. Additionally, Pluto also goes much slower in its orbit compared to Earth. Both of these factors contribute to the longer orbital period of Pluto.

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• 45.

### A woman on the surface of the Earth has a mass of 50 kilograms and a weight of 490 newtons. If the woman were floating freely inside a space habitat far away from Earth, she would have

• A.

Less weight and more mass.

• B.

Less weight and the same mass.

• C.

Less weight and less mass.

• D.

More weight and less mass.

• E.

None of these

B. Less weight and the same mass.
Explanation
When the woman is on the surface of the Earth, she experiences the force of gravity, which gives her a weight of 490 newtons. However, if she were floating freely inside a space habitat far away from Earth, she would be outside the influence of Earth's gravity and therefore would not experience any weight. However, her mass would remain the same at 50 kilograms, as mass is a measure of the amount of matter an object contains and is independent of gravity. Therefore, the correct answer is that she would have less weight and the same mass.

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• 46.

### A "weightless" astronaut in an orbiting shuttle is

• A.

Shielded from the Earth's gravitational field.

• B.

Beyond the pull of gravity.

• C.

Pulled only by gravitation to the shuttle which cancels the Earth's gravitational pull.

• D.

Like the shuttle, pulled by Earth's gravitation.

• E.

None of these

D. Like the shuttle, pulled by Earth's gravitation.
Explanation
In this scenario, the astronaut is considered "weightless" because they are in freefall around the Earth. Although they may feel weightless, they are still being pulled by the Earth's gravitational force, just like the shuttle they are in. Therefore, the correct answer is that the astronaut is like the shuttle, pulled by Earth's gravitation.

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• 47.

### Consider a moon that orbits one of our most distant planets in an elliptical path. The distance that the moon covers each day is

• A.

Greatest when the moon is closest to the planet.

• B.

Greatest when the moon is furthest from the planet.

• C.

The same regardless of its distance from the sun.

• D.

The same regardless of its distance from the planet.

A. Greatest when the moon is closest to the planet.
Explanation
The distance that the moon covers each day is greatest when the moon is closest to the planet because an elliptical path means that the moon's distance from the planet is not constant. When the moon is closest to the planet, it is subject to a stronger gravitational pull, causing it to move faster and cover a greater distance in a day compared to when it is further away.

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• 48.

### A satellite describes an elliptical orbit about a planet. The satellite travels much faster when it is directly over a

• A.

Large ocean.

• B.

Large island.

• C.

High mountain range.

• D.

Great plain or plateau.

• E.

None of the above choices affects its speed very much.

E. None of the above choices affects its speed very much.
Explanation
The speed of a satellite is primarily determined by its distance from the planet and its mass. The presence of a large ocean, island, mountain range, plain, or plateau does not significantly affect these factors. Therefore, none of the above choices would have a significant impact on the satellite's speed.

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• 49.

### Our moon travels the fastest as it orbits the Earth when it is

• A.

Performing an eclipse.

• B.

Rotating.

• C.

Revolving.

• D.

Closest.

• E.

All of the above choices are true.

D. Closest.
Explanation
The moon travels the fastest when it is closest to the Earth because of the gravitational pull between the two bodies. As the moon gets closer to the Earth, the gravitational force increases, causing the moon to accelerate and move faster in its orbit.

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• 50.

### A lunar month is about 28 days. If the moon were farther from the Earth than it is now, the lunar month would be

• A.

More than 28 days.

• B.

Less than 28 days.

• C.

• D.

Difficult to predict without much more information.

A. More than 28 days.
Explanation
If the moon were farther from the Earth, it would take longer for the moon to complete its orbit around the Earth. This means that the time it takes for the moon to go through its phases, which is roughly a month, would also be longer. Therefore, the lunar month would be more than 28 days if the moon were farther from the Earth.

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• Current Version
• Mar 22, 2023
Quiz Edited by
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• Nov 30, 2012
Quiz Created by
Drtaylor

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