Chapter 2: Describing Motion: Kinematics In One Dimension
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Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled.
A.
The displacement is either greater than or equal to the distance traveled.
B.
The displacement is always equal to the distance traveled.
C.
The displacement is either less than or equal to the distance traveled.
D.
The displacement can be either greater than, smaller than, or equal to the distance
traveled.
Correct Answer C. The displacement is either less than or equal to the distance traveled.
Explanation The displacement is either less than or equal to the distance traveled because displacement refers to the change in position from the starting point to the ending point, regardless of the path taken. The distance traveled, on the other hand, refers to the total length of the path taken. In some cases, the displacement may be less than the distance traveled if the object takes a longer route or changes direction multiple times. However, it can also be equal to the distance traveled if the object travels in a straight line from start to finish.
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2.
When is the average velocity of an object equal to the instantaneous velocity?
A.
Always
B.
Never
C.
Only when the velocity is constant
D.
Only when the velocity is increasing at a constant rate
Correct Answer C. Only when the velocity is constant
Explanation The average velocity of an object is equal to the instantaneous velocity only when the velocity is constant. This means that the object is moving at a consistent speed and in a straight line without any changes in direction. In such cases, the average velocity over a given time interval will be the same as the velocity at any specific moment within that interval. However, if the velocity is changing, either in magnitude or direction, the average velocity will not be equal to the instantaneous velocity.
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3.
A new car manufacturer advertises that their car can go "from zero to sixty in 8 s". This is a description of
A.
Average speed.
B.
Instantaneous speed.
C.
Average acceleration.
D.
Instantaneous acceleration.
Correct Answer C. Average acceleration.
Explanation The statement "from zero to sixty in 8 s" describes the average acceleration of the car. Average acceleration is calculated by dividing the change in velocity (from zero to sixty) by the time taken (8 seconds). This description indicates how quickly the car can increase its velocity over a specific time interval, which is average acceleration.
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4.
An object moving in the +x axis experiences an acceleration of 2.0 m/s^2. This means the object is
A.
Traveling at 2.0 m in every second.
B.
Traveling at 2.0 m/s in every second.
C.
Changing its velocity by 2.0 m/s.
D.
Increasing its velocity by 2.0 m/s in every second.
Correct Answer D. Increasing its velocity by 2.0 m/s in every second.
Explanation The given information states that the object is experiencing an acceleration of 2.0 m/s^2. Acceleration is the rate of change of velocity, so if the object is experiencing an acceleration of 2.0 m/s^2, it means its velocity is increasing by 2.0 m/s every second. Therefore, the correct answer is "increasing its velocity by 2.0 m/s in every second."
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5.
Suppose that a car traveling to the East (+x direction) begins to slow down as it approaches a traffic light. Make a statement concerning its acceleration.
A.
The car is decelerating, and its acceleration is positive.
B.
The car is decelerating, and its acceleration is negative.
C.
The acceleration is zero.
D.
A statement cannot be made using the information given.
Correct Answer B. The car is decelerating, and its acceleration is negative.
Explanation The given statement indicates that the car is slowing down, which means its velocity is decreasing. Since acceleration is the rate of change of velocity, a negative acceleration is required to cause a decrease in velocity. Therefore, the correct answer is that the car is decelerating, and its acceleration is negative.
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6.
Suppose that a car traveling to the West (-x direction) begins to slow down as it approaches a traffic light. Make a statement concerning its acceleration.
A.
The car is decelerating, and its acceleration is positive.
B.
The car is decelerating, and its acceleration is negative.
C.
The acceleration is zero.
D.
A statement cannot be made using the information given.
Correct Answer A. The car is decelerating, and its acceleration is positive.
Explanation The car is decelerating because it is slowing down. Since the car is traveling in the negative x direction (West), its acceleration is also negative. However, because deceleration is a negative acceleration, the negative sign cancels out and the acceleration is considered positive.
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7.
Suppose that an object is moving with a constant velocity. Make a statement concerning its acceleration.
A.
The acceleration must be constantly increasing.
B.
The acceleration must be constantly decreasing.
C.
The acceleration must be a constant non-zero value.
D.
The acceleration must be equal to zero.
Correct Answer D. The acceleration must be equal to zero.
Explanation If an object is moving with a constant velocity, it means that its speed and direction are not changing. In order for acceleration to be present, there must be a change in velocity. Since the object's velocity is not changing, the acceleration must be equal to zero.
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8.
If the velocity of an object is zero, does it mean that the acceleration is zero? Support your answer with an example.
A.
No, and an example would be an object starting from rest
B.
No, and an example would be an object coming to a stop
C.
Yes, because of the way in which velocity is defined
D.
Yes, because of the way in which acceleration is defined
Correct Answer A. No, and an example would be an object starting from rest
Explanation The correct answer is no. When the velocity of an object is zero, it does not necessarily mean that the acceleration is zero. An example that supports this is an object starting from rest. In this case, the object initially has zero velocity, but it experiences an acceleration to increase its velocity over time. Therefore, the velocity is zero, but the acceleration is not.
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9.
Can an object's velocity change direction when its acceleration is constant? Support your answer with an example.
A.
No, this is not possible because it is always speeding up.
B.
No, this is not possible because it is always speeding up or always slowing down, but it
can never turn around.
C.
Yes, this is possible, and a rock thrown straight up is an example.
D.
Yes, this is possible, and a car that starts from rest, speeds up, slows to a stop, and then
backs up is an example.
Correct Answer C. Yes, this is possible, and a rock thrown straight up is an example.
Explanation The correct answer is "Yes, this is possible, and a rock thrown straight up is an example." This is because when a rock is thrown straight up, its velocity changes direction while its acceleration remains constant. Initially, the rock is accelerating upwards due to the force applied to it. As it reaches its maximum height, the velocity becomes zero, and then it starts accelerating downwards due to the force of gravity. Therefore, even though the acceleration remains constant, the velocity changes direction.
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10.
Suppose that an object is moving with constant acceleration. Make a statement concerning its motion with respect to time.
A.
In equal times its speed increases by equal amounts.
B.
In equal times its velocity changes by equal amounts.
C.
In equal times it moves equal distances.
D.
A statement cannot be made using the information given.
Correct Answer B. In equal times its velocity changes by equal amounts.
Explanation The correct answer is "In equal times its velocity changes by equal amounts." This statement is true because when an object is moving with constant acceleration, its velocity changes by the same amount in equal time intervals. This means that the object's speed increases or decreases at a constant rate over time.
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11.
Can an object have increasing speed while its acceleration is decreasing? Support your answer with an example.
A.
No, this is impossible because of the way in which acceleration is defined.
B.
No, because if acceleration is decreasing the object will be slowing down.
C.
Yes, and an example would be an object falling in the absence of air friction.
D.
Yes, and an example would be an object released from rest in the presence of air friction.
Correct Answer D. Yes, and an example would be an object released from rest in the presence of air friction.
Explanation Yes, an object can have increasing speed while its acceleration is decreasing. An example of this is an object released from rest in the presence of air friction. Initially, the object experiences a high acceleration due to gravity, but as it gains speed, the air friction increases, causing the acceleration to decrease. However, the object's speed continues to increase until it reaches a terminal velocity where the air friction force matches the gravitational force.
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12.
Suppose a can, after an initial kick, moves up along a smooth hill of ice. Make a statement concerning its acceleration.
A.
It will travel at constant velocity with zero acceleration.
B.
It will have a constant acceleration up the hill, but a different constant acceleration when it
comes back down the hill.
C.
It will have the same acceleration, both up the hill and down the hill.
D.
It will have a varying acceleration along the hill.
Correct Answer C. It will have the same acceleration, both up the hill and down the hill.
Explanation The correct answer is that the can will have the same acceleration, both up the hill and down the hill. This is because acceleration is determined by the net force acting on an object, and in this case, the only force acting on the can is gravity. Since gravity acts in the same direction regardless of whether the can is moving up or down the hill, the acceleration remains constant.
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13.
Under what condition is average velocity equal to the average of the object's initial and final velocity?
A.
The acceleration must be constantly changing.
B.
The acceleration must be constant.
C.
This can only occur if there is no acceleration.
D.
This is impossible.
Correct Answer B. The acceleration must be constant.
Explanation When the acceleration is constant, the average velocity of an object over a certain time interval is equal to the average of its initial and final velocity. This is because when the acceleration is constant, the object's velocity changes at a constant rate. Therefore, the average velocity can be calculated by taking the average of the initial and final velocity.
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14.
Objects A and B both start at rest. They both accelerate at the same rate. However, object A accelerates for twice the time as object B. What is the final speed of object A compared to that of object B?
A.
The same speed
B.
Twice as fast
C.
Three times as fast
D.
Four times as fast
Correct Answer B. Twice as fast
Explanation Since both objects accelerate at the same rate, the final speed of an object is directly proportional to the time it accelerates. In this case, object A accelerates for twice the time as object B. Therefore, object A will have twice the final speed compared to object B.
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15.
Objects A and B both start from rest. They both accelerate at the same rate. However, object A accelerates for twice the time as object B. What is the distance traveled by object A compared to that of object B?
A.
The same distance
B.
Twice as far
C.
Three times as far
D.
Four times as far
Correct Answer D. Four times as far
Explanation Object A accelerates for twice the time as object B. Since both objects have the same acceleration, the longer duration of acceleration for object A means that it will reach a higher final velocity compared to object B. As a result, object A will cover a greater distance in the same amount of time compared to object B. Therefore, the distance traveled by object A is four times as far as that of object B.
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16.
When an object is released from rest and falls in the absence of friction, which of the following is true concerning its motion?
A.
The speed of the falling object is proportional to its mass.
B.
The speed of the falling object is proportional to its weight.
C.
The speed of the falling object is inversely proportional to its surface area.
D.
None of the above is true.
Correct Answer D. None of the above is true.
Explanation The correct answer is None of the above is true. When an object is released from rest and falls in the absence of friction, the speed of the falling object is not proportional to its mass or weight. The speed of the falling object is also not inversely proportional to its surface area. In reality, in the absence of friction, all objects fall at the same rate regardless of their mass or weight, which is known as the principle of equivalence. This is explained by the gravitational force acting on the object being independent of its mass or weight.
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17.
When an object is released from rest and falls in the absence of friction, which of the following is true concerning its motion?
A.
Its acceleration is constant.
B.
Its velocity is constant.
C.
Neither its acceleration nor its velocity is constant.
D.
Both its acceleration and its velocity are constant.
Correct Answer A. Its acceleration is constant.
Explanation When an object is released from rest and falls in the absence of friction, its acceleration is constant. This is because the only force acting on the object is gravity, which causes a constant acceleration towards the ground. The velocity of the object increases continuously as it falls, but its acceleration remains constant throughout the motion.
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18.
Suppose a ball is thrown straight up. Make a statement about the velocity and the acceleration when the ball reaches the highest point.
A.
Both its velocity and its acceleration are zero.
B.
Its velocity is zero and its acceleration is not zero.
C.
Its velocity is not zero and its acceleration is zero.
D.
Neither its velocity nor its acceleration is zero.
Correct Answer B. Its velocity is zero and its acceleration is not zero.
Explanation When the ball reaches the highest point, its velocity is zero because it momentarily stops moving before it starts falling back down. However, its acceleration is not zero because gravity is still acting on the ball, pulling it downwards. The acceleration due to gravity is constant and always acts in the downward direction, even when the ball is at its highest point.
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19.
Suppose a ball is thrown straight up. What is its acceleration just before it reaches its highest point?
A.
Zero
B.
Slightly less than g
C.
Exactly g
D.
Slightly greater than g
Correct Answer C. Exactly g
Explanation The acceleration of the ball just before it reaches its highest point is exactly g. This is because at the highest point of its trajectory, the ball momentarily comes to a stop before reversing its direction and falling back down. At this point, the acceleration due to gravity is the only force acting on the ball, pulling it back towards the ground at a constant rate of g, which is approximately 9.8 m/s^2.
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20.
Suppose a ball is thrown straight up, reaches a maximum height, then falls to its initial height. Make a statement about the direction of the velocity and acceleration as the ball is going up.
A.
Both its velocity and its acceleration point upward.
B.
Its velocity points upward and its acceleration points downward.
C.
Its velocity points downward and its acceleration points upward.
D.
Both its velocity and its acceleration points downward.
Correct Answer B. Its velocity points upward and its acceleration points downward.
Explanation As the ball is going up, its velocity points upward because it is moving in the opposite direction of gravity. However, its acceleration points downward because gravity is constantly pulling it downward, causing it to slow down and eventually reverse direction. Therefore, the correct answer is that its velocity points upward and its acceleration points downward.
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21.
A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Make a statement about the direction of the velocity and acceleration as the ball is coming down.
A.
Both its velocity and its acceleration point upward.
B.
Its velocity points upward and its acceleration points downward.
C.
Its velocity points downward and its acceleration points upward.
D.
Both its velocity and its acceleration point downward.
Correct Answer D. Both its velocity and its acceleration point downward.
Explanation As the ball is coming down, its velocity is directed downward because it is moving in the opposite direction of the initial throw. Additionally, its acceleration is also directed downward because gravity is pulling the ball downward, causing it to accelerate towards the ground. Therefore, both the velocity and acceleration of the ball point downward.
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22.
Suppose a ball is thrown downward in the absence of air resistance. Make a statement concerning its acceleration.
A.
Its acceleration is constantly increasing.
B.
Its acceleration is constant.
C.
Its acceleration is constantly decreasing.
D.
Its acceleration is zero.
Correct Answer B. Its acceleration is constant.
Explanation In the absence of air resistance, the only force acting on the ball is gravity. According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Since the mass of the ball remains constant and the force of gravity is constant, the acceleration of the ball remains constant as well. Therefore, the correct statement is that its acceleration is constant.
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23.
Suppose a skydiver jumps from a high-flying plane. What is her acceleration when she she reaches terminal velocity?
A.
It is essentially zero.
B.
It is in the upward direction.
C.
It is approximately 9.8 m/s^2 downward.
D.
It is a constant pointing upward.
Correct Answer A. It is essentially zero.
Explanation When a skydiver reaches terminal velocity, it means that the force of gravity pulling her downward is balanced by the air resistance pushing upward. At this point, the net force on the skydiver is zero, which means there is no acceleration. Therefore, her acceleration when she reaches terminal velocity is essentially zero.
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24.
A ball is thrown vertically upward with a speed v. An identical second ball is thrown upward with a speed 2v (twice as fast). What is the ratio of the maximum height of the second ball to that of the first ball? (How many times higher does the second ball go than the first ball?)
A.
4:1
B.
2:1
C.
1.7:1
D.
1.4:1
Correct Answer A. 4:1
Explanation The ratio of the maximum height of the second ball to that of the first ball is 4:1. This is because the maximum height reached by a vertically thrown ball is directly proportional to the square of its initial velocity. Since the second ball is thrown with twice the initial velocity of the first ball, its maximum height will be four times higher than that of the first ball. Therefore, the ratio is 4:1.
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25.
Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the distance between them
A.
Increases.
B.
Remains constant.
C.
Decreases.
D.
Cannot be determined from the information given.
Correct Answer A. Increases.
Explanation As time progresses, the distance between the two balls increases because both balls are subject to the same gravitational force and acceleration. Since ball B is dropped one second after ball A, it starts its descent from a lower height and therefore takes more time to reach the ground. As a result, ball A has a head start and is able to cover more distance in the same amount of time, leading to an increasing distance between the two balls.
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26.
Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the difference in their speeds
A.
Increases.
B.
Remains constant.
C.
Decreases.
D.
Cannot be determined from the information given.
Correct Answer B. Remains constant.
Explanation The explanation for the correct answer "remains constant" is that both balls are dropped from the same building, which means they experience the same acceleration due to gravity. This acceleration remains constant throughout the motion, regardless of the time at which the balls were dropped. Therefore, the difference in their speeds will remain constant as well.
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27.
Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street?
A.
The one thrown up is traveling faster.
B.
The one thrown down is traveling faster.
C.
They are traveling at the same speed.
D.
It is impossible to tell because the height of the building is not given.
Correct Answer C. They are traveling at the same speed.
Explanation The two objects have the same initial speed, so they will experience the same acceleration due to gravity as they fall towards the ground. This means that their speeds will be the same when they hit the street. The height of the building is not relevant in determining their speeds, as it only affects the time it takes for them to reach the ground.
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28.
A brick is dropped from the top of a building. A second brick is thrown straight down from the same building. They are released at the same time. Neglect air resistance. Compare the accelerations of the two bricks.
A.
The first brick accelerates faster.
B.
The second brick accelerates faster.
C.
The two bricks accelerate at the same rate.
D.
It is impossible to determine from the information given.
Correct Answer C. The two bricks accelerate at the same rate.
Explanation The acceleration of an object in free fall near the surface of the Earth is constant and equal to the acceleration due to gravity, which is approximately 9.8 m/s^2. Since both bricks are released at the same time and neglecting air resistance, they will experience the same acceleration due to gravity. Therefore, the correct answer is that the two bricks accelerate at the same rate.
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29.
An object is moving with constant non-zero velocity in the +x axis. The position versus time graph of this object is
A.
A horizontal straight line.
B.
A vertical straight line.
C.
A straight line making an angle with the time axis.
D.
A parabolic curve.
Correct Answer C. A straight line making an angle with the time axis.
Explanation The correct answer is a straight line making an angle with the time axis. When an object is moving with constant non-zero velocity in the +x axis, its position versus time graph will be a straight line. The angle that this straight line makes with the time axis represents the velocity of the object.
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30.
An object is moving with constant non-zero acceleration in the +x axis. The position versus time graph of this object is
A.
A horizontal straight line.
B.
A vertical straight line.
C.
A straight line making an angle with the time axis.
D.
A parabolic curve.
Correct Answer D. A parabolic curve.
Explanation When an object is moving with constant non-zero acceleration in the +x axis, its position versus time graph will be a parabolic curve. This is because the object's velocity is constantly changing due to the acceleration, resulting in a curved trajectory. The steeper the curve, the greater the acceleration. Therefore, a parabolic curve is the correct representation of the position versus time graph for an object with constant non-zero acceleration in the +x axis.
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31.
An object is moving with constant non-zero velocity in the +x axis. The velocity versus time graph of this object is
A.
A horizontal straight line.
B.
A vertical straight line.
C.
A straight line making an angle with the time axis.
D.
A parabolic curve.
Correct Answer A. A horizontal straight line.
Explanation The object is moving with constant non-zero velocity in the +x axis, which means its velocity does not change over time. This is represented by a horizontal straight line on the velocity versus time graph. Since the velocity is constant, there is no acceleration, and therefore the graph does not show any change in velocity over time.
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32.
An object is moving with constant non-zero acceleration in the +x axis. The velocity versus time graph of this object is
A.
A horizontal straight line.
B.
A vertical straight line.
C.
A straight line making an angle with the time axis.
D.
A parabolic curve.
Correct Answer C. A straight line making an angle with the time axis.
Explanation The correct answer is a straight line making an angle with the time axis. This is because when an object is moving with constant non-zero acceleration, its velocity increases or decreases at a constant rate. This results in a linear relationship between velocity and time, represented by a straight line. The angle of the line with the time axis represents the rate of change of velocity over time, which is the acceleration.
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33.
The slope of a position versus time graph gives
A.
Position.
B.
Velocity.
C.
Acceleration.
D.
Displacement.
Correct Answer B. Velocity.
Explanation The slope of a position versus time graph represents the rate at which an object's position is changing over time. This rate is known as velocity, which is the speed and direction of an object's motion. Therefore, the correct answer is velocity.
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34.
The slope of a velocity versus time graph gives
A.
Position.
B.
Velocity.
C.
Acceleration.
D.
Displacement.
Correct Answer C. Acceleration.
Explanation The slope of a velocity versus time graph gives the rate of change of velocity, which is acceleration. This is because acceleration is defined as the change in velocity per unit time. Therefore, the correct answer is acceleration.
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35.
The area under a curve in an acceleration versus time graph gives
A.
Acceleration.
B.
Velocity.
C.
Displacement.
D.
Position.
Correct Answer B. Velocity.
Explanation The area under a curve in an acceleration versus time graph gives the change in velocity. This is because acceleration is the rate of change of velocity, so integrating the acceleration over time gives the change in velocity. Therefore, the correct answer is velocity.
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36.
The area under a curve in a velocity versus time graph gives
A.
Acceleration.
B.
Velocity.
C.
Displacement.
D.
Position.
Correct Answer C. Displacement.
Explanation The area under a curve in a velocity versus time graph represents the change in position or displacement. This is because the area under the curve represents the total distance traveled by an object over a certain time period. Since displacement is the change in position, it is the most appropriate interpretation of the area under the curve in this context. Acceleration, velocity, and position are not directly related to the area under the curve in a velocity versus time graph.
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37.
If the position versus time graph of an object is a horizontal line, the object is
A.
Moving with constant non-zero speed.
B.
Moving with constant non-zero acceleration.
C.
At rest.
D.
Moving with infinite speed.
Correct Answer C. At rest.
Explanation If the position versus time graph of an object is a horizontal line, it means that the object is not changing its position over time. This indicates that the object is at rest, as it is not moving in any direction.
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38.
If the position versus time graph of an object is a vertical line, the object is
A.
Moving with constant non-zero speed.
B.
Moving with constant non-zero acceleration.
C.
At rest.
D.
Moving with infinite speed.
Correct Answer D. Moving with infinite speed.
Explanation If the position versus time graph of an object is a vertical line, it means that the object's position is not changing with time. This indicates that the object is at rest and not moving at all. Therefore, the correct answer is "at rest."
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39.
If the velocity versus time graph of an object is a horizontal line, the object is
A.
Moving with constant non-zero speed.
B.
Moving with constant non-zero acceleration.
C.
At rest.
D.
Moving with infinite speed.
Correct Answer A. Moving with constant non-zero speed.
Explanation If the velocity versus time graph of an object is a horizontal line, it means that the velocity of the object is not changing over time. This indicates that the object is moving with a constant speed, as there is no acceleration present. The fact that the speed is non-zero means that the object is not at rest, and it is not moving with infinite speed as that would require an infinite slope on the graph.
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40.
If the velocity versus time graph of an object is a straight line making an angle of 30 degrees with the time axis, the object is
A.
Moving with constant non-zero speed.
B.
Moving with constant non-zero acceleration.
C.
At rest.
D.
Moving with infinite speed.
Correct Answer B. Moving with constant non-zero acceleration.
Explanation If the velocity versus time graph of an object is a straight line making an angle of 30 degrees with the time axis, it indicates that the object is moving with a constant non-zero acceleration. This is because the slope of the velocity versus time graph represents the acceleration of the object. Since the graph is a straight line, it means that the acceleration is constant. Additionally, the fact that the line makes an angle of 30 degrees with the time axis suggests that the acceleration is non-zero.
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41.
An object moves 15.0 m north and then 11.0 m south. Find both the distance traveled and the magnitude of the displacement vector.
A.
6.0 m, 26.0 m
B.
26.0 m, 6.0 m
C.
26.0 m, 26.0 m
D.
6.0 m, 6.0 m
Correct Answer B. 26.0 m, 6.0 m
Explanation The distance traveled is the sum of the distances traveled in each direction, which is 15.0 m + 11.0 m = 26.0 m. The magnitude of the displacement vector is the straight-line distance between the starting point and the ending point, which is the absolute value of the difference between the distances traveled in each direction, which is |15.0 m - 11.0 m| = 4.0 m. Therefore, the correct answer is 26.0 m, 6.0 m.
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42.
A boat can move at 30 km/h in still water. How long will it take to move 12 km upstream in a river flowing 6.0 km/h?
A.
20 min
B.
22 min
C.
24 min
D.
30 min
Correct Answer D. 30 min
Explanation The boat is moving upstream, which means it is moving against the direction of the river flow. The speed of the boat in still water is 30 km/h, and the speed of the river flow is 6 km/h. To find the time it takes to move 12 km upstream, we can use the formula Time = Distance / Speed. The effective speed of the boat when moving upstream is the difference between its speed in still water and the speed of the river flow, which is 30 km/h - 6 km/h = 24 km/h. Using the formula, we get Time = 12 km / 24 km/h = 0.5 hours, which is equal to 30 minutes. Therefore, it will take 30 minutes for the boat to move 12 km upstream.
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43.
55 mi/h is how many m/s?
(1 mi = 1609 m.)
A.
25 m/s
B.
49 m/s
C.
90 m/s
D.
120 m/s
Correct Answer A. 25 m/s
Explanation To convert miles per hour (mi/h) to meters per second (m/s), we need to multiply the given value by a conversion factor. The conversion factor is 1609 m/1 mi since 1 mile is equal to 1609 meters. By multiplying 55 mi/h by the conversion factor, we get 55 mi/h * 1609 m/1 mi = 88,495 m/h. To convert this to m/s, we need to divide by 3600 (since there are 3600 seconds in an hour). Therefore, 88,495 m/h / 3600 s/h = 24.58 m/s, which can be rounded to 25 m/s.
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44.
What must be your average speed in order to travel 350 km in 5.15 h?
A.
66.0 km/h
B.
67.0 km/h
C.
68.0 km/h
D.
69.0 km/h
Correct Answer C. 68.0 km/h
Explanation To calculate average speed, we divide the total distance traveled by the total time taken. In this case, the total distance is 350 km and the total time is 5.15 hours. Dividing 350 by 5.15 gives us approximately 67.96 km/h. Since speed is usually rounded to the nearest whole number, the correct answer is 68.0 km/h.
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45.
A runner ran the marathon (approximately 42.0 km) in 2 hours and 57 min. What is the average speed of the runner in m/s?
A.
14.2 * 10^3 m/s
B.
124 m/s
C.
3.95 m/s
D.
14.2 m/s
Correct Answer C. 3.95 m/s
Explanation The average speed of the runner can be calculated by dividing the total distance covered by the time taken. In this case, the runner covered a distance of approximately 42.0 km, which is equal to 42,000 meters. The time taken was 2 hours and 57 minutes, which is equal to 177 minutes. To convert this to seconds, we multiply by 60, giving us 10,620 seconds. Dividing the distance by the time, we get an average speed of approximately 3.95 m/s.
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46.
A car travels 90 km/h. How long does it take for it to travel 400 km?
A.
4.1 h
B.
4.2 h
C.
4.3 h
D.
4.4 h
Correct Answer D. 4.4 h
Explanation The car is traveling at a speed of 90 km/h. To find the time it takes for the car to travel 400 km, we divide the distance by the speed. 400 km divided by 90 km/h equals approximately 4.4 hours. Therefore, it takes the car 4.4 hours to travel 400 km.
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47.
A ly (light year) is the distance that light travels in one year. The speed of light is 3.00 * 10^8 m/s. How many miles are there in a ly?
(1 mi = 1609 m, 1 yr = 365 d.)
A.
9.46 * 10^12 mi
B.
9.46 * 10^15 mi
C.
5.88 * 10^12 mi
D.
5.88 * 10^15 mi
Correct Answer C. 5.88 * 10^12 mi
Explanation The speed of light is given as 3.00 * 10^8 m/s. To find the distance in miles, we need to convert this speed from meters to miles. We know that 1 mile is equal to 1609 meters. Therefore, we can calculate the distance in miles by dividing the speed of light in meters by 1609.
3.00 * 10^8 m/s / 1609 m = 1.86 * 10^5 mi/s
Next, we need to find the distance traveled in one year. We know that there are 365 days in a year. Therefore, we can multiply the speed in miles per second by the number of seconds in a day (24 hours * 60 minutes * 60 seconds) and then multiply by 365.
If you are driving 72 km/h along a straight road and you look to the side for 4.0 s, how far do you travel during this inattentive period?
A.
18 m
B.
20 m
C.
40 m
D.
80 m
Correct Answer D. 80 m
Explanation When driving at a constant speed of 72 km/h, the distance traveled can be calculated by multiplying the speed by the time. In this case, the time is given as 4.0 seconds. To convert the speed from km/h to m/s, divide it by 3.6. So, 72 km/h is equal to 20 m/s. Multiplying the speed by the time gives us 20 m/s * 4 s = 80 m. Therefore, during the 4.0-second period of inattention, the driver travels a distance of 80 meters.
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49.
If you run a complete loop around an outdoor track (400 m), in 100 s, your average velocity is
A.
0.25 m/s.
B.
4.0 m/s.
C.
40,000 m/s.
D.
Zero.
Correct Answer D. Zero.
Explanation If you run a complete loop around an outdoor track in 100 seconds, your average velocity is zero because velocity is defined as the change in position divided by the change in time. Since you end up back at your starting position after running a complete loop, the change in position is zero, resulting in an average velocity of zero.
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50.
A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, then 1.0 km north, then 1.0 km west to return to its starting point. This trip takes 45 min. What was the bear's average speed?
A.
0 km/h
B.
0.09 km/h
C.
4.5 km/h
D.
5.3 km/h
Correct Answer D. 5.3 km/h
Explanation The polar bear traveled a total distance of 4.0 km (1.0 km south + 1.0 km east + 1.0 km north + 1.0 km west). Since the trip took 45 minutes, we need to convert the time to hours by dividing it by 60. Therefore, the average speed of the bear is calculated by dividing the distance (4.0 km) by the time (45/60 hours), which equals 5.3 km/h.
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