1.
One possible unit of speed is
Correct Answer
D. All of the above
Explanation
The correct answer is "all of the above" because each option listed - miles per hour, light years per century, and kilometers per hour - can be used as units of speed. Miles per hour is commonly used in the United States, kilometers per hour is commonly used in many other countries, and light years per century is used to measure the speed of light over long distances in astronomical calculations. Therefore, all three options are valid units of speed.
2.
When you look at the speedometer in a moving car, ou can see the car's
Correct Answer
D. Instantanious speed
Explanation
When you look at the speedometer in a moving car, you can see the car's instantaneous speed. The speedometer measures the current speed of the car at any given moment. It provides a real-time reading of how fast the car is currently moving, allowing the driver to maintain a desired speed or adjust their driving accordingly. The other options, such as average distance traveled, average speed, average acceleration, and instantaneous acceleration, are not directly indicated by the speedometer.
3.
Acceleration is defined as the CHANGE in
Correct Answer
D. Velocity divided by the time interval
Explanation
Acceleration is defined as the rate at which an object's velocity changes over time. It is calculated by dividing the change in velocity by the time interval. Therefore, the correct answer is "velocity divided by the time interval". This formula allows us to measure how quickly an object's velocity is changing, regardless of the distance it has traveled or the time it takes to move from one place to another.
4.
A car starts from rest and after 7 sec. it is moving at 42 m/s. what is the car's average acceleration?
Correct Answer
A. 0.17 m/s^2
Explanation
The average acceleration of a car can be calculated by dividing the change in velocity by the time taken. In this case, the car starts from rest and reaches a velocity of 42 m/s in 7 seconds. The change in velocity is 42 m/s - 0 m/s = 42 m/s. Dividing this by 7 seconds gives an average acceleration of 6 m/s^2. Therefore, the correct answer is 6 m/s^2.
5.
As an object falls freely in a vacuum,its
Correct Answer
C. Both a and b
Explanation
When an object falls freely in a vacuum, its velocity increases because it is constantly accelerating due to the force of gravity. The acceleration of the object also increases because the force of gravity remains constant, causing the object to gain more speed with each passing second. Therefore, both the velocity and acceleration of the object increase as it falls freely in a vacuum.
6.
In the absense of air resistance,objects fall at constant
Correct Answer
E. All of the above
Explanation
In the absence of air resistance, objects fall at a constant acceleration due to gravity. This means that their speed increases at a constant rate as they fall. Additionally, their velocity also increases at a constant rate, as velocity is the combination of speed and direction. The distance traveled by the object also increases with each successive speed, as the object covers a greater distance in each unit of time. Therefore, all of the above options - speed, velocity, acceleration, and distance each successive speed - are correct explanations for the behavior of falling objects in the absence of air resistance.
7.
Suppose an object isd in free fall. each second the object falls
Correct Answer
B. A larger distance than the second before
Explanation
As the object is in free fall, it is subjected to the force of gravity, causing it to accelerate. This means that its speed increases with each passing second. Since the object is accelerating, it covers a larger distance in each subsequent second compared to the previous second. Therefore, the correct answer is that it falls a larger distance than the second before.
8.
If you drop a feather and a coin at the same time in a tube filled with air,which will reach the bottom first
Correct Answer
B. Neither_ they will both reach the bottom at the same time
Explanation
The feather and the coin will both reach the bottom at the same time because in the presence of air, the force of gravity acting on both objects is the same. However, if the experiment is conducted in a vacuum where there is no air resistance, the coin would reach the bottom first due to its higher mass and greater resistance to air resistance.
9.
Consider drops of water leaking from the water fauset. as the drops fall they
Correct Answer
B. Get farther
Explanation
As the drops of water fall from the water faucet, they get farther apart. This can be observed by the increasing distance between each successive drop. The force of gravity causes the drops to accelerate downwards, resulting in a larger gap between them as they fall. Therefore, the correct answer is "get farther."
10.
Suppose you take a trip that covers 180 km and takes 3 hours to make. your average speed is
Correct Answer
B. 60 km/h
Explanation
The average speed is calculated by dividing the total distance traveled by the total time taken. In this case, the total distance is 180 km and the total time taken is 3 hours. So, 180 km divided by 3 hours gives an average speed of 60 km/h.
11.
A ball is thrown straight up. At the top of its path its instantaneious speed is
Correct Answer
B. About 5m/s
Explanation
When a ball is thrown straight up, its instantaneous speed at the top of its path is not zero because it still has some upward velocity. It is also not 10 m/s, 20 m/s, or 50 m/s because the ball is slowing down due to the force of gravity. Therefore, the most accurate answer is that the instantaneous speed at the top of its path is about 5 m/s.
12.
A car accelerates at 2 m/s^2. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?
Correct Answer
B. 10 sec
Explanation
The car is accelerating at a constant rate of 2 m/s^2. To find the time it takes to accelerate to a speed of 20 m/s, we can use the formula v = u + at, where v is the final velocity, u is the initial velocity (which is 0 in this case), a is the acceleration, and t is the time. Rearranging the formula, we have t = (v - u) / a. Plugging in the values, we get t = (20 - 0) / 2 = 10 seconds. Therefore, the correct answer is 10 sec.
13.
If a freely falling object were somehow equipped with a speedometer,its speed reading would increase each second by
Correct Answer
D. A variable amount
14.
A freely falling object starts from res. after falling for 6 sec, it will have a speed of about
Correct Answer
C. 60 m/s
Explanation
When an object is in free fall, it accelerates due to gravity. The acceleration due to gravity is approximately 9.8 m/s^2. After falling for 6 seconds, the object will have reached a speed of 9.8 m/s^2 * 6 s = 58.8 m/s. Since the answer options are rounded, the closest option is 60 m/s.
15.
A freely falling object starts from rest. After falling for 1 sec, it will have a speed of about
Correct Answer
B. 10 m/s
Explanation
When an object falls freely, it accelerates due to gravity. The acceleration due to gravity is approximately 9.8 m/s^2. After falling for 1 second, the object would have accelerated to a speed of approximately 9.8 m/s. However, since the object starts from rest, it would have an additional speed of 0 m/s. Therefore, the total speed of the object after falling for 1 second would be approximately 9.8 m/s, which is closest to the given answer of 10 m/s.
16.
Suppose a jumper claims a hang time of 2 sec. then that jumper must be able to jump vertical distance of
Correct Answer
E. 5 m
Explanation
If a jumper claims a hang time of 2 seconds, it means that they are able to stay in the air for that duration. Hang time is directly related to the vertical distance jumped. The longer the hang time, the higher the jumper can go. Therefore, if the jumper claims a hang time of 2 seconds, it indicates that they are able to jump a vertical distance of 5 meters.
17.
A vector is a quantity that has
Correct Answer
C. Magnitude and direction
Explanation
A vector is a quantity that has both magnitude and direction. Magnitude refers to the size or length of the vector, while direction indicates the orientation or angle at which the vector is pointing. Therefore, a vector must have both magnitude and direction to fully describe its characteristics. Time is not a characteristic of a vector, as it does not affect its magnitude or direction.
18.
A scalar is a quantity that has
Correct Answer
A. Direction
Explanation
A scalar is a quantity that does not have direction. It only has magnitude, which represents the size or amount of the quantity. Direction is a characteristic of vector quantities, which have both magnitude and direction. Therefore, the correct answer is "direction."
19.
Whichof the following would not be considered a projectle?
Correct Answer
B. A cannonball rolling down a slope
Explanation
A cannonball rolling down a slope would not be considered a projectile because it is in contact with the ground and is being influenced by the force of gravity and the slope. In order to be considered a projectile, an object must be launched into the air with an initial velocity and then follow a curved path under the influence of gravity, without any other forces acting on it. The cannonball rolling down a slope is not following a curved path and is being influenced by the slope, so it does not meet the criteria to be considered a projectile.
20.
The hortizontal component of a projectile's velocity is independent of
Correct Answer
C. The vertical component of its velocity
Explanation
The horizontal component of a projectile's velocity is determined solely by the initial velocity and the angle at which it was launched. It is not affected by the vertical component of its velocity, as the two components are independent of each other. Therefore, changing the vertical component of the velocity will not alter the horizontal component or the range of the projectile. Similarly, time does not affect the horizontal component of velocity, as it only affects the vertical motion of the projectile.
21.
In absence of air friction, the hortizontal component of a projectile's velocity doesnt change as the projectile moves.
Correct Answer
B. Always true
Explanation
In the absence of air friction, the horizontal component of a projectile's velocity remains constant because there are no external forces acting on it in the horizontal direction. This means that the projectile will continue to move horizontally at the same speed throughout its trajectory. Therefore, the statement is always true.
22.
At the instant a ball is thrown hortizontally with a large force, an identical ball is dropped from the same height. which ball hits the ground first?
Correct Answer
A. Neither. they both will hit the ground at the same time
Explanation
The horizontal force does not affect the time it takes for an object to fall vertically. Both balls will experience the same acceleration due to gravity and will take the same amount of time to reach the ground. Therefore, neither ball will hit the ground first.
23.
In the absence of air resistance, the angle at which a thrown ball will go the farthest is
Correct Answer
C. 45 degrees
Explanation
The correct answer is 45 degrees because this angle allows for the optimal combination of horizontal and vertical components of the ball's motion. At 45 degrees, the ball will have the maximum range because it will spend an equal amount of time in the air traveling horizontally and vertically. This angle ensures that the ball covers the greatest horizontal distance before hitting the ground.