# Chapter 10 Prelecture

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question
A
Gravitational potential energy is... A. mass times the acceleration due to gravity times vertical position. B. velocity per unit mass. C. the area under a gravity force-versus-time graph. D. the gravitation constant times mass-squared divided by distance-squared. C. 1/2 mass times speed-squared.
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3
Mechanical energy is 1 the energy due to internal moving parts. 2 the energy of motion. 3 the sum of kinetic energy plus potential energy. 4 the energy of position. 5 the sum of kinetic, potential, thermal, and elastic energy.
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5
For conservative forces, Force can be found as being the negative of the derivative of 1 kinetic energy. 2 momentum. 3 work. 4 impulse. 5 potential energy.
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B
Rank in order, from largest to smallest, the gravitational potential energies of the balls. A 1 > 2 = 4 > 3 B 3 > 2 = 4 > 1 C 3 > 2 > 4 > 1 D 1 > 2 > 3 > 4
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3
As the projectile goes upward, what energy changes take place? 1 Both kinetic and potential energy decrease. 2 Both kinetic and potential energy increase. 3 Kinetic energy decreases; potential energy increases. 4 Kinetic energy increases; potential energy decreases.
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4
At the top point of the flight, what can be said about the projectile's kinetic and potential energy? 1 Both kinetic and potential energy are at their maximum values. 2 Both kinetic and potential energy are at their minimum values. 3 Kinetic energy is at a maximum; potential energy is at a minimum. 4 Kinetic energy is at a minimum; potential energy is at a maximum.
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4
The potential energy of the object at the moment of launch __________. 1 is negative 2 is positive 3 is zero 4 depends on the choice of the "zero level" of potential energy
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3
Suppose our experimenter repeats his experiment on a planet more massive than Earth, where the acceleration due to gravity is g=30 m/s2. When he releases the ball from chin height without giving it a push, how will the ball's behavior differ from its behavior on Earth? 1 It will take more time to return to the point from which it was released. 2 Its mass will be greater. 3 It will take less time to return to the point from which it was released. 4 It will smash his face. 5 It will stop well short of his face.
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2
The force acting on the particle at point A is __________. 1 directed to the right 2 directed to the left 3 equal to zero
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1
The force acting on the particle at point C is __________. 1 directed to the right 2 directed to the left 3 equal to zero
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3
The force acting on the particle at point B is __________. 1 directed to the right 2 directed to the left 3 equal to zero
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3
The acceleration of the particle at point B is __________. 1 directed to the right 2 directed to the left 3 equal to zero
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2
If the particle is located slightly to the left of point B, its acceleration is __________. 1 directed to the right 2 directed to the left 3 equal to zero
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1
If the particle is located slightly to the right of point B, its acceleration is __________. 1 directed to the right 2 directed to the left 3 equal to zero
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BF
Name all labeled points on the graph corresponding to unstable equilibrium.
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DH
Name all labeled points on the graph corresponding to stable equilibrium.
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BDFH
Name all labeled points on the graph where the acceleration of the particle is zero.
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AE
Name all labeled points such that when a particle is released from rest there, it would accelerate to the left.
question
A
Consider points A, E, and G. Of these three points, which one corresponds to the greatest magnitude of acceleration of the particle?
question
D
What point on the graph corresponds to the maximum kinetic energy of the moving particle?
question
B
At what point on the graph does the particle have the lowest speed?
question
X
At which of the three points labeled in the figure is the magnitude of the force on the particle greatest?
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4
Which, if any, of the following statements concerning the work done by a conservative force is NOT true? 1 It can always be expressed as the difference between the initial and final values of a potential energy function. 2 When the starting and ending points are the same, the total work is zero. 3 It is independent of the path of the body and depends only on the starting and ending points. 4 All of the above statements are true.
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N
If the force on a particle at some point in space is zero, must its potential energy also be zero at that point? Y/N
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N
If the potential energy of a particle at some point in space is zero, must the force on it also be zero at that point? Y/N
question
C
A roller-coaster car rolls down a frictionless track, reaching speed v_0 at the bottom. If you want the car to go twice as fast at the bottom, by what factor must you increase the height of the track? A You must increase the track height by a factor of 2. B You must increase the track height by a factor of 3. C You must increase the track height by a factor of 4.
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N
Can kinetic energy ever be negative? Y/N
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Y
Can gravitational potential energy ever be negative? Y/N
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3
Is it possible for a system to have negative potential energy? 1 Yes, as long as the total energy is positive. 2 No, because this would have no physical meaning. 3 Yes, since the choice of the zero of potential energy is arbitrary. 4 Yes, as long as the kinetic energy is positive. 5 No, because the kinetic energy of a system must equal its potential energy.
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2
Upon what basic quantity does kinetic energy depend? 1 Position 2 Motion 3 Size 4 Force
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4
Upon what basic quantity does potential energy depend? 1 Force 2 Size 3 Motion 4 Position
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1/4
The same ball is shot straight up a second time from the same gun, but this time the spring is compressed only half as far before firing. How far up does the ball go this time?
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2
The work-energy theorem states that a force acting on a particle as it moves over a ______ changes the ______ energy of the particle if the force has a component parallel to the motion. 1 distance / potential 2 distance / kinetic 3 vertical displacement / potential 4 none of the above
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3