1.
Science is a body of knowledge that
Correct Answer
D. All of the above choices are correct
Explanation
Science is a body of knowledge that encompasses all of the above choices. It not only condenses knowledge into testable laws but also describes order in nature. Additionally, science is an ongoing activity of humans, as it is constantly evolving and expanding our understanding of the world around us. Therefore, all of the given choices are correct in describing science.
2.
As an object freely falls downward, its
Correct Answer
B. Velocity increases
Explanation
As an object freely falls downward, its velocity increases. This is because the object is subject to the force of gravity, which causes it to accelerate. As time passes, the object's speed increases, resulting in an increase in velocity. Therefore, the correct answer is that the velocity increases.
3.
A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. This best demonstrates that
Correct Answer
A. The milk carton has inertia
Explanation
The fact that the milk carton does not topple when the paper is jerked quickly suggests that the milk carton has inertia. Inertia is the tendency of an object to resist changes in its state of motion. In this case, the milk carton resists the change in its position when the paper is pulled out quickly, indicating that it has inertia. The other options are not applicable in this scenario.
4.
The gain in speed each second for a freely-falling object is about
Correct Answer
D. 10 m/s
Explanation
The gain in speed each second for a freely-falling object is about 10 m/s. This is because in free fall, the object experiences a constant acceleration due to gravity of approximately 9.8 m/sÂ². This means that its speed increases by 9.8 m/s every second. Since the question asks for an approximate value, 10 m/s is a reasonable answer.
5.
A package falls of a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is
Correct Answer
D. About 30 m/s
Explanation
The horizontal speed of the package just before it hits the ground is about 30 m/s because the package falls vertically due to gravity, while the truck continues to move horizontally at a constant speed of 30 m/s. Since there is no force acting horizontally on the package, its horizontal speed remains the same as the truck's speed. Therefore, the package will have a horizontal speed of about 30 m/s just before it hits the ground.
6.
According to Newton's law of inertia, a rail road train in motion should continue going forever even if its engine is turned off. We never observe this because railroad trains.
Correct Answer
D. Always have forces that oppose their motion
Explanation
According to Newton's law of inertia, an object in motion will continue moving in a straight line at a constant speed unless acted upon by an external force. In the case of a railroad train, there are always forces that oppose its motion, such as friction between the wheels and the tracks, air resistance, and the force of gravity. These opposing forces eventually slow down and stop the train, even if its engine is turned off. Therefore, we never observe a railroad train in motion forever because there are always forces acting against its motion.
7.
A scientific statement that can never be changed is a scientific
Correct Answer
E. None of the above choices are correct
Explanation
The given question asks for a scientific statement that can never be changed. However, none of the options provided (principle, theory, hypothesis, law) fit this criteria. In science, all statements are subject to change and revision based on new evidence and discoveries. Therefore, none of the given choices are correct.
8.
If no external forces are acting on a moving object it will
Correct Answer
A. Continue moving at the same velocity
Explanation
If no external forces are acting on a moving object, it will continue moving at the same velocity. This is because according to Newton's first law of motion, an object in motion will stay in motion with the same velocity unless acted upon by an external force. In the absence of any external forces, there is no force to slow down or stop the object, so it will continue moving with the same velocity.
9.
Galileo's use of inclined planes allowed him to effectively
Correct Answer
C. Slow down the acceleration of free fall
Explanation
Galileo's use of inclined planes allowed him to slow down the acceleration of free fall. By placing objects on inclined planes, Galileo was able to reduce the effect of gravity on their motion, resulting in a slower acceleration. This enabled him to study and measure the effects of gravity more accurately, as he could observe the motion of objects at a slower pace. Inclined planes provided a controlled environment for Galileo to conduct experiments and gather data, contributing to his understanding of the laws of motion and gravity.
10.
The two measurements necessary for calculating average speed are
Correct Answer
E. Distance and time
Explanation
To calculate average speed, we need to know the distance traveled and the time it took to cover that distance. Distance is the total length of the path traveled, while time is the duration of the journey. By dividing the distance by the time taken, we can determine the average speed. Acceleration and velocity are not directly used in calculating average speed, although they may be relevant in other calculations such as determining changes in speed over time.
11.
A horse gallops a distance of 10 kilometers in a time of 30 minutes. It's average speed is
Correct Answer
C. 20 km/h
Explanation
The average speed of an object is calculated by dividing the total distance traveled by the time taken. In this case, the horse galloped a distance of 10 kilometers in a time of 30 minutes. To find the average speed, we divide 10 kilometers by 0.5 hours (since there are 60 minutes in an hour and 30 minutes is equal to 0.5 hours). The result is 20 kilometers per hour, which means that the horse's average speed is 20 km/h.
12.
A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval it acceleration is
Correct Answer
A. Zero
Explanation
When a car maintains a constant velocity, it means that its speed is not changing. In other words, the car is not accelerating or decelerating. Acceleration is the rate at which an object's velocity changes over time. Since the car's velocity is constant at 100 km/hr for 10 seconds, there is no change in velocity, and therefore the acceleration is zero.
13.
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected the force required to keep the puck sliding at constant velocity is
Correct Answer
B. Zero
Explanation
The force required to keep the puck sliding at a constant velocity is zero. This is because if ice friction and air resistance are neglected, there are no external forces acting on the puck to slow it down or change its velocity. Therefore, no force is needed to maintain its constant velocity.
14.
Twelve seconds after starting from rest, an object falling freely will have a speed of
Correct Answer
D. More than 100 m/s
Explanation
When an object falls freely under the influence of gravity, it accelerates at a constant rate of 9.8 m/s^2. After 12 seconds, the object would have been accelerating for a significant amount of time, resulting in a high velocity. Since the options provided are 50 m/s, 100 m/s, 10 m/s, and "more than 100 m/s," the correct answer would be "more than 100 m/s" as the object would have gained a substantial speed due to the acceleration.
15.
If an object moves with constant acceleration, its velocity must
Correct Answer
B. Change by the same amount each second
Explanation
If an object moves with constant acceleration, its velocity must change by the same amount each second. This is because acceleration is defined as the rate of change of velocity. Therefore, if the acceleration is constant, the change in velocity will also be constant over time.
16.
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
Correct Answer
B. Directed downward
Explanation
The acceleration of the ball is directed downward because when the ball is tossed vertically upward, it experiences a gravitational force pulling it downward. As the ball rises, the force of gravity slows it down until it reaches its highest point, where its velocity momentarily becomes zero. As the ball falls back down, the force of gravity accelerates it in the downward direction, causing its velocity to increase. Therefore, throughout the entire motion, the acceleration of the ball is always directed downward, opposite to its initial upward velocity.
17.
If a car accelerates form rest at 2 meters per second per second, its speed 3 seconds later will be about
Correct Answer
B. 6 m/s
Explanation
The car is accelerating at a constant rate of 2 meters per second per second. This means that its speed is increasing by 2 meters per second every second. After 3 seconds, the car's speed will have increased by 2 meters per second three times, resulting in a speed of 6 meters per second.
18.
At on instant an object in free fall is moving downward at 50 meters per second. One second later is speed should be about
Correct Answer
D. 60 m/s
Explanation
When an object is in free fall, it experiences a constant acceleration due to gravity. This acceleration is approximately 9.8 m/s^2. Since the object is moving downward at 50 m/s, after one second its speed should increase by 9.8 m/s. Therefore, the speed of the object should be approximately 60 m/s.
19.
Starting from rest, the distance a freely-falling object will fall in 1.0 second is about
Correct Answer
C. 5.0 m
Explanation
When an object is freely falling, it accelerates due to gravity at a rate of 9.8 m/s^2. In the first second of free fall, the object will accelerate to a velocity of 9.8 m/s. Using the equation for distance traveled during constant acceleration (d = 1/2 * a * t^2), where a is the acceleration and t is the time, we can calculate the distance fallen. Plugging in the values, we get d = 1/2 * 9.8 * 1^2 = 4.9 m. Therefore, the closest answer is 5.0 m.
20.
An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. After 5 seconds, the object will have a speed of
Correct Answer
E. 100 m/s
Explanation
On a planet where the acceleration due to gravity is 20 meters per second squared, the object will experience a constant acceleration as it falls freely. The speed of an object under constant acceleration can be calculated using the equation v = u + at, where v is the final velocity, u is the initial velocity (which is 0 in this case as the object starts from rest), a is the acceleration, and t is the time. Plugging in the values, we get v = 0 + (20 m/s^2)(5 s) = 100 m/s. Therefore, after 5 seconds, the object will have a speed of 100 m/s.
21.
If you drop an object, it will accelerate downward at a rate of 9.8 meters per second per second. If you instead throw it downwards, its acceleration (in the absence of air resistance and after it leaves your hand) will be
Correct Answer
C. 9.8 meters per second per second
Explanation
When an object is dropped, it falls freely under the influence of gravity. Gravity causes the object to accelerate downward at a constant rate of 9.8 meters per second per second. When an object is thrown downwards, it still experiences the same gravitational force, resulting in the same acceleration of 9.8 meters per second per second. Therefore, the correct answer is 9.8 meters per second per second.
22.
If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about
Correct Answer
A. 2 seconds
Explanation
When a projectile is fired straight up, it follows a parabolic path due to the force of gravity. The initial velocity of 10 m/s determines the upward motion, while gravity causes it to slow down and eventually reverse direction. Since the time it takes for the projectile to reach its highest point and fall back down is the same, the total time to return to its starting position is twice the time it takes to reach the highest point. Therefore, the total time is approximately 2 seconds.
23.
When a rock thrown straight upwards gets tot he exact top of its path, its
Correct Answer
C. Velocity is zero and its acceleration is about 10 meters per second per second
Explanation
When a rock thrown straight upwards reaches the exact top of its path, its velocity is zero because it momentarily stops moving in that direction. However, its acceleration is about 10 meters per second per second because gravity is still acting on the rock, causing it to accelerate downwards even though its velocity is momentarily zero. This is due to the constant acceleration due to gravity, which is approximately 10 meters per second per second near the Earth's surface.
24.
A ball is thrown upwards. Neglecting air resistance, what initial upward speed does the ball need to remain in the air for a total time of 10 seconds?
Correct Answer
E. About 50 m/s
Explanation
To remain in the air for a total time of 10 seconds, the ball needs to reach its maximum height and then fall back down to the ground within that time frame. The time it takes for the ball to reach its maximum height is half of the total time, so 10/2 = 5 seconds. The initial upward speed needed to reach the maximum height can be calculated using the equation v = u + at, where v is the final velocity (0 m/s at the maximum height), u is the initial velocity, a is the acceleration (due to gravity, which is -9.8 m/s^2), and t is the time taken (5 seconds). Rearranging the equation, u = v - at, we get u = 0 - (-9.8 * 5) = 49 m/s. Therefore, the initial upward speed needed for the ball to remain in the air for a total time of 10 seconds is about 50 m/s.
25.
Which has a greater mass?
Correct Answer
A. An automobile battery
Explanation
An automobile battery has a greater mass compared to a king-size pillow. This is because an automobile battery is typically made of lead-acid and is designed to provide a significant amount of power to start a car's engine. The lead plates and other components in the battery contribute to its overall mass. On the other hand, a king-size pillow is usually filled with lightweight materials such as feathers, foam, or synthetic fibers, which make it much lighter in comparison. Therefore, the automobile battery has a greater mass than the king-size pillow.
26.
Strange as it may seem, it is just as hard to accelerate a car on a level surface on the oon as it is here on the Earth. This is because
Correct Answer
B. The mass of the car is independent of gravity
Explanation
The correct answer is that the mass of the car is independent of gravity. This means that the mass of an object remains the same regardless of the gravitational force acting on it. Therefore, the difficulty in accelerating a car on the moon is not due to the mass of the car, but rather the lower gravitational force compared to Earth.
27.
The newton is a unit of
Correct Answer
A. Force
Explanation
The newton is a unit of force. It is named after Sir Isaac Newton and is defined as the amount of force required to accelerate a one-kilogram mass by one meter per second squared. Force is a vector quantity that can cause an object to accelerate, decelerate, or change its direction of motion. It is measured in newtons and is commonly encountered in everyday life, such as when pushing or pulling objects, or the force exerted by gravity on a mass.
28.
A rock weighs 30 N on Earth. A second rock weighs 30 N on the moon. Which of the two rocks has the greater mass? (gravity on the moon is one-sixth of that on Earth)
Correct Answer
A. The one on the moon
Explanation
The weight of an object depends on the gravitational force acting on it. Since the weight of the rock on the moon is 30 N, which is one-sixth of its weight on Earth, it means that the gravitational force acting on the rock on the moon is one-sixth of the gravitational force acting on the rock on Earth. Therefore, the rock on the moon has a smaller gravitational force acting on it, indicating that it has a smaller mass compared to the rock on Earth. Hence, the correct answer is "the one on the moon."
29.
A 10-kg brick and 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is
Correct Answer
D. 10 times as much
Explanation
The force of gravity on an object is directly proportional to its mass. In this scenario, the 10-kg brick has a greater mass than the 1-kg book. Therefore, the force of gravity on the 10-kg brick is 10 times as much as the force on the 1-kg book.
30.
The force of friction on a sliding object is 10 newtons. The applied force needed to maintain a constant velocity is
Correct Answer
C. 10 N
Explanation
The applied force needed to maintain a constant velocity is equal to the force of friction. In this case, the force of friction is given as 10 newtons, so the applied force needed to maintain a constant velocity is also 10 newtons.
31.
Whenever the net force on an object is zero, its acceleration
Correct Answer
A. Is zero
Explanation
When the net force on an object is zero, it means that all the forces acting on the object are balanced and cancel each other out. In this case, according to Newton's second law of motion, the acceleration of the object will be zero. This is because acceleration is directly proportional to the net force acting on the object. If the net force is zero, there is no resultant force to cause acceleration, hence the acceleration will be zero.
32.
A 1-kg mass at the earth's surface weighs
Correct Answer
D. 9.8 N
Explanation
The weight of an object is the force exerted on it due to gravity. At the earth's surface, the acceleration due to gravity is approximately 9.8 m/s^2. Since weight is equal to mass multiplied by acceleration due to gravity, a 1-kg mass at the earth's surface would weigh 9.8 N.
33.
A 10-N falling object encounters 4 N of air resistance. The net force on the object is
Correct Answer
C. 6 N
Explanation
The net force on the object is 6 N. This is because the net force is the difference between the force of gravity (10 N) and the force of air resistance (4 N). By subtracting the force of air resistance from the force of gravity, we find that the net force is 6 N.
34.
An object is propelled along a straight-line path by a force. If the net force were doubled, the object's acceleration would be
Correct Answer
C. Twice as much
Explanation
When the net force acting on an object is doubled, according to Newton's second law of motion (F = ma), the acceleration of the object will also double. This is because acceleration is directly proportional to the net force applied to an object. Therefore, if the net force is doubled, the object's acceleration will also double.
35.
An object is propelled along a straight-line path in space by a force. If the mass of the object somehow becomes twice as much, its acceleration
Correct Answer
A. Halves
Explanation
When the mass of an object is doubled, its acceleration will halve. This can be explained by Newton's second law of motion, which states that the acceleration of an object is directly proportional to the force applied to it and inversely proportional to its mass. Therefore, if the force remains constant and the mass doubles, the acceleration will decrease by half. This is because the increased mass requires more force to achieve the same acceleration.
36.
Hang from a pair of gym rings and the upward support forces of the rings will always
Correct Answer
B. Add up to equal your weight
Explanation
When hanging from a pair of gym rings, the upward support forces of the rings will add up to equal your weight. This is because the rings provide an equal and opposite force to counteract the downward force of your weight. Therefore, the combined upward forces of the rings will balance out and be equal to your weight.
37.
A tow truck exerts a force of 3000 N on a car, accelerating it at 2 meters per second per second. What is the mass of the car?
Correct Answer
A. 1500 kg
Explanation
The force exerted by the tow truck on the car is given as 3000 N. According to Newton's second law of motion, force is equal to mass multiplied by acceleration. The acceleration of the car is given as 2 meters per second per second. Rearranging the formula, we can find the mass of the car by dividing the force by the acceleration. Therefore, the mass of the car is 3000 N / 2 m/s^2 = 1500 kg.
38.
An object following a straight-line path at constant speed
Correct Answer
A. Has zero acceleration
Explanation
An object following a straight-line path at constant speed has zero acceleration because acceleration is the rate of change of velocity, and if the velocity is constant, there is no change in velocity over time. Therefore, the object's acceleration is zero.
39.
Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction from the first force. The particle with both forces acting on it
Correct Answer
D. Continues at the speed it had when it encountered the second force
Explanation
When a particle is being accelerated through space by a 10-N force and encounters a second force of 10 N in the opposite direction, the two forces cancel each other out. As a result, there is no net force acting on the particle. According to Newton's first law of motion, an object will continue to move at a constant velocity unless acted upon by an external force. Therefore, the particle will continue at the speed it had when it encountered the second force.
40.
The brakes of a speeding truck are slammed on and it skids to a stop. If the truck were heavily loaded so that it had twice the total mass, the skidding distance would be
Correct Answer
E. The same
Explanation
When the brakes are slammed on, the skidding distance of the truck depends on its mass. According to Newton's second law of motion, the force required to stop an object is directly proportional to its mass. Therefore, if the truck is heavily loaded and has twice the total mass, it will require twice the force to stop it. However, the frictional force between the tires and the road, which is responsible for the skidding, is also directly proportional to the mass of the truck. As a result, the increased force required to stop the heavily loaded truck is balanced by the increased frictional force, resulting in the same skidding distance as the unloaded truck.
41.
If you are driving at 20 m/s and slam on your brakes and skid at 0.5 g (5m/s/s) to a full stop, the skidding time in seconds is
Correct Answer
C. About 4
Explanation
When you slam on your brakes and skid to a full stop, the skidding time can be calculated using the formula t = v/a, where t is the time, v is the initial velocity, and a is the acceleration. In this case, the initial velocity is 20 m/s and the acceleration is 5 m/s/s (0.5g). Plugging these values into the formula, we get t = 20/5 = 4 seconds. Therefore, the skidding time is about 4 seconds.
42.
If more horizontal force is applied to a sliding object than is needed to maintain a constant velocity,
Correct Answer
C. The object accelerates in the direction of the applied force
Explanation
When more horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object will accelerate in the direction of the applied force. This is because the applied force is greater than the opposing force of friction, causing the object to accelerate in the same direction as the force.