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Is it correct to say that all changes in the physical world involve energy transformations of some sort? Why? |
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2 | |
Under what circumstances (if any) is no work done on a moving object even though a net force acts upon it? |
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3 | |
In what part of its orbit is the earth's potential energy greatest with respect to the sun? In what part of its orbit is the earth's kinetic energy greatest? Explain your answers. |
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4 | |
Does every moving body possess kinetic energy? Does every stationary body possess potential energy? |
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5 | |
A golf ball and a Ping-Pong ball are dropped in a vacuum chamber. When they have fallen halfway to the bottom, how do their speeds compare? Their kinetic energies? Their potential energies? Their momenta? |
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6 | |
The potential energy of a golf ball in a hole is negative with respect to the ground. Under what circumstances (if any) is the ball's kinetic energy negative? Its rest energy? |
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7 | |
Two identical balls move down a tilted board. Ball A slides down without friction and ball B rolls down. Which ball reaches the bottom first? Why? |
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8 | |
The kilowatt-hour is a unit of what physical quantity or quantities? |
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9 | |
Why does a nail become hot when it is hammered into a piece of wood? |
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10 | |
As we will learn in Chap. 5, electric charges of the same kind (both positive or both negative) repel each other, whereas charges of opposite sign (one positive and the other negative) attract each other. (a) What happens to the PE of a positive charge when it is brought near another positive charge? (b) When it is brought near a negative charge? |
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11 | |
Is it possible for an object to have more kinetic energy but less momentum than another object? Less kinetic energy but more momentum? |
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12 | |
What happens to the momentum of a car when it comes to a stop? |
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13 | |
When the kinetic energy of an object is doubled, what happens to its momentum? |
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14 | |
What, if anything, happens to the speed of a fighter plane when it fires a cannon at an enemy plane in front of it? |
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An empty dump truck coasts freely with its engine off along a level road. (a) What happens to the truck's speed if it starts to rain and water collects in it? (b) The rain stops and the accumulated water leaks out. What happens to the truck's speed now? |
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A railway car is at rest on a frictionless track. A man at one end of the car walks to the other end. (a) Does the car move while he is walking? (b) If so, in which direction? (c) What happens when the man comes to a stop? |
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If the polar ice caps melt, the length of the day will increase. Why? |
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18 | |
The unusual weather pattern called El Niño (see Sec. 13-7) involves a slowing down of the normal easterly winds near the equator and a speeding up of westerly winds such as the jet streams. As a result the entire atmosphere moves faster than usual in the direction of the earth's rotation. Would you expect this to affect the length of the day? If so, why and in what way? |
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19 | |
What are the two postulates from which Einstein developed the special theory of relativity? |
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20 | |
What physical quantity will all observers always find the same value for? |
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21 | |
The length of a rod is measured by several observers, one of whom is stationary with respect to the rod. What must be true of the value obtained by the stationary observer? |
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22 | |
If the speed of light were smaller than it is, would relativistic phenomena be more or less conspicious than they are now? |
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23 | |
(a) In the formula E0 = m0c2 for rest energy, what does the symbol c represent? (b) What is the difference between m0 and m? |
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24 | |
Why is it impossible for an object to move faster than the speed of light? |
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25 | |
What is the effect on the law of conservation of energy of the discovery that matter and energy can be converted into each other? |
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26 | |
Which three fuels provide most of the world's energy today? |
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27 | |
What energy sources, if any, cannot be traced to sunlight falling on the earth? |
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28 | |
What are some of the disadvantages shared by all renewable-energy sources such as solar cells and windmills? |
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