Physics ch. 9

In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m? 1) 50 J. 2) 5 J 3) 10 J 4) 15 J

1) 50 J.

What is the magnitude of the gravitational force between two 1-kg bodies that are 1 m apart? 1. 6.67 × 10 -11 N 2. 1 kg 3. 6.67 × 10 -11 kg 4. 10 N

1. 6.67 × 10 -11 N

Black holes are essentially _______. 1. collapsed stars 2. the vacuum cleaners of space 3. very dark stars 4. not confirmed as existing

1. collapsed stars

When the useful energy output of a simple machine is 100 J, and the total energy input is 200 J, the efficiency is _______. 1) 200 % 2) 50 %. 3) 75 %. 4) 100 %.

2) 50 %.

Approximately how much time passes between low and high tide? 1) 4 hours 2) 6 hours 3) 12 hours 4) 24 hours

2) 6 hours

Calculate the force of gravity on the 1-kg mass if it were 1.3×10^7 m above Earth's surface (that is, if it were three Earth radii from Earth's center). F=G(m1m2/d^2)

F = 1.1 N

What would the magnitude of the gravitational field be anywhere inside a hollow, spherical planet? 1. The same as the surface value 2. Half the surface value 3. Zero N/kg 4. A quarter of the surface value

3. Zero N/kg

When traveling twice as fast your kinetic energy is increased _______. 1. not at all. 2. by two. 3. by four. 4. by three.

3. by four.

Energy cannot be _______. 1. transferred, transformed, or destroyed. 2. transformed. 3. transferred. 4. destroyed.

4. destroyed.

Fossil fuels, hydroelectric power, and wind power ultimately get their energy from _______. 1. the Sun 2. greenhouse gases 3. potential energy 4. Earth's nuclear energy.

1. the Sun

When one does twice the work in twice the time, the power expended is _______. 1. twice as much. 2. the same. 3. three times as much 4. four times as much

2. the same.

Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________. 1. greater than your normal weight at rest 2. equal to your normal weight at rest 3. less than your normal weight at rest

3. less than your normal weight at rest Even though the elevator is still moving upward, the fact that its speed is slowing means that the acceleration is downward; the situation is rather like that of a ball that is still on its way up after you throw it, even though it is being pulled downward with the acceleration of gravity. Because the acceleration of the elevator is downward, your weight is lower than normal.

Which two factors mainly affect ocean tides on Earth? Check two answers. 1. the pull of distant planets 2. Earth's revolution about both the Moon and the Sun 3. the Sun 4. the Moon

3. the Sun 4. the Moon

Einstein's theory of gravitation, compared with Newton's, _______. 1. more greatly emphasizes the inverse-square law 2. enhances the role of force 3. is one and the same 4. eliminates the role of force

4. eliminates the role of force

Find the change in the gravitational force between two planets if the masses of both planets are doubled but the distance between them stays the same.

Fnew/F = 4

What happens to the force of attraction between two planets when the distance between them is doubled? 1. The force decreases to half. 2. The force decreases to one quarter. 3. The force remains the same. 4. The force doubles.

2. The force decreases to one quarter.

Earth's gravitational field is strongest at _______. 1. infinity, in principle 2. either the Earth's center or at its surface 3. Earth's surface 4. Earth's center

3. Earth's surface

The work that is done when twice the load is lifted twice the distance is _______. 1. three times as much 2. the same. 3. four times as much. 4. twice as much.

3. four times as much.

Which of the following lists correctly gives, in increasing order, the height of the high tides that occur during particular lunar phases? (Ties are denoted by parentheses.) 1. (first quarter, third quarter), (new, full) 2. first quarter, third quarter, full, new 3. new, full, first quarter, third quarter 4. (new, full), (first quarter, third quarter)

1. (first quarter, third quarter), (new, full) Neap tides occur during first-quarter and third-quarter lunar phases (with equal strength), and spring tides occur during new moon and full moon phases (with equal strength).

If Earth shrank, but there was no change in its mass, then what would happen to your weight at the surface? 1. It would increase. 2. It would decrease at first and then increase. 3. It would stay the same. 4. It would decrease.

1. It would increase.

A high tide can occur __________. 1. when the Moon is high overhead 2. when the Moon is low in the sky (setting or rising) 3. only when the Moon is full

1. when the Moon is high overhead Because the tidal bulges on Earth are always directed towards the Moon (and directly away from the Moon on the far side of Earth), the Moon must be high in the sky during a high tide, and low tides occur when the Moon is setting or rising.

From Part B, you know that from afar we'll never see the in-falling rocket cross the event horizon, yet it will still eventually disappear from view. Why? 1. Even though you won't see it cross the event horizon, it does cross it and that means you can no longer see it. 2. Its light will become so redshifted that it will be undetectable. 3. The black hole's blackness will drown out the light of the rocket. 4. Tidal forces will squeeze the in-falling rocket to an undetectably thin line.

2. Its light will become so redshifted that it will be undetectable. As the animation shows, viewed from afar the light of the in-falling rocket becomes increasingly redshifted. As it approaches the event horizon, the redshift approaches infinity, meaning all its light is stretched to such enormous wavelengths that no detector could see it, even in principle.

From the viewpoint of an observer in the orbiting rocket, what happens to time on the other rocket as it falls toward the event horizon of the black hole? 1. Time runs increasingly faster as the rocket approaches the black hole. 2. Time runs increasingly slower as the rocket approaches the black hole. 3. Time is always the same on both rockets.

2. Time runs increasingly slower as the rocket approaches the black hole. In this animation, our view is similar to the view from the orbiting rocket. Notice that the clock on the falling rocket ticks more slowly as it approaches the black hole, indicating that time is slowing down.

If there were no Moon, would there still be tides on Earth? 1. No, the Moon is essential to our tides. 2. Yes, because the Sun's gravity still has an influence. 3. Yes, because the Earth is still rotating.

2. Yes, because the Sun's gravity still has an influence. The Sun exerts a tidal force that is roughly one-third the tidal force of the Moon, so the tides would be smaller, but there would still be tides.

If you were inside the rocket that falls toward the event horizon, you would notice your own clock to be running __________. 1. increasingly faster as you approach the event horizon 2. at a constant, normal rate as you approach the event horizon 3. increasingly slower as you approach the event horizon

2. at a constant, normal rate as you approach the event horizon All motion is relative, and you will always consider your own clock to be running at a normal rate.

If you are standing on a scale in an elevator, what exactly does the scale measure? 1. your mass 2. the force you exert on the scale 3. the gravitational force exerted on you by Earth

2. the force you exert on the scale You probably recognize that neither your mass nor the gravitational force exerted on you change when you are in an elevator. The scale measures the force that is exerted on it, which in an elevator is a combination of the force due to your normal weight and a force due to the elevator's acceleration.

Each day _______________. 1. there is one high tide and one low tide 2. there are two high tides and two low tides 3. there are three high tides and three low tides 4. the number of tides depends on the seasons

2. there are two high tides and two low tides The tidal force of the Moon produces two tidal bulges, so as the Earth rotates the shoreline will pass through both tidal bulges in a 24-hour period, causing two high tides.

Why are all tides greatest at the time of a full Moon or new Moon? 1. At full Moon and new Moon, the tides from the Moon and the Sun partially cancel because they are in line with Earth. 2. At full Moon and new Moon, the tides from the Moon and the Sun partially cancel because they make a right angle with Earth. 3. At full Moon and new Moon, the tides from the Moon and the Sun add because they are in line with Earth. 4. At full Moon and new Moon, the tides from the Moon and the Sun add because they make a right angle with Earth.

3. At full Moon and new Moon, the tides from the Moon and the Sun add because they are in line with Earth.

Why does the gravity in the Space Shuttle compare with the gravity on Earth the way it does? 1. The Space Shuttle is much farther away from the center of the Earth than the surface of the Earth. 2. The Space Shuttle is much closer to the center of the Earth than the surface of the Earth. 3. The Space Shuttle is about the same distance from the center of the Earth than from the surface of the Earth.

3. The Space Shuttle is about the same distance from the center of the Earth than from the surface of the Earth.

What happens to the force of attraction between two planets when the masses of both are doubled? 1. The force remains the same. 2. The force doubles. 3. The force quadruples. 4. The force increases by 16.

3. The force quadruples.

How does the gravity in the Space Shuttle compare with the gravity on Earth's surface? 1. The gravity in the Space Shuttle is much larger than the gravity on Earth's surface. 2. The gravity in the Space Shuttle is much smaller than the gravity on Earth's surface. 3. The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.

3. The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.

Where do you weigh more: at the bottom of Death Valley or atop one of the peaks of the Sierra Nevada? Why? 1. You weigh more on the summit because the air buoys you up less. 2. You weigh more in Death Valley because more atmosphere pushes down on you. 3. You weigh more in Death Valley because you are closer to the center of Earth. 4. You weigh more on the summit, because the higher you go, the harder you fall.

3. You weigh more in Death Valley because you are closer to the center of Earth.

If you were inside the rocket that falls toward the event horizon, from your own viewpoint you would __________. 1. slow down and come to a stop at the event horizon 2. slow down and cross the event horizon at low speed 3. accelerate as you fall and cross the event horizon completely unhindered

3. accelerate as you fall and cross the event horizon completely unhindered From your point of view, time runs normally in your spaceship and gravity must accelerate you as you fall toward the black hole. There is no physical barrier at the event horizon, so you cross it unhindered.

Isaac Newton synthesized _______. 1. the pulls of the planets on one another 2. the extent to which gravity extends in the universe 3. terrestrial and cosmic laws 4. the pulls of the Moon and Earth

3. terrestrial and cosmic laws

What Newton discovered most about gravity is that it is _______. 1. another rule of nature, though an important one 2. the strongest of known forces 3. universal 4. ever present

3. universal

What was the cause of perturbations discovered in the orbit of the planet Uranus? What later discovery did this lead to? 1. Pluto caused the perturbations, and later Neptune was discovered. 2. Pluto caused the perturbations, and later Einstein's theory of gravitation was discovered. 3. Neptune caused the perturbations, and later Newton's law of universal gravitation was discovered. 4. Neptune caused the perturbations, and later Pluto was discovered.

4. Neptune caused the perturbations, and later Pluto was discovered.

Which energy production method does not ultimately depend on the Sun? 1. Photovoltaic cells. 2. Fossil fuels 3. Wind power 4. Nuclear fission

4. Nuclear fission

As you found in Part A, your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight? 1. The elevator moves upward with constant velocity. 2. The elevator moves downward with constant velocity. 3. The elevator moves upward while slowing in speed. 4. The elevator moves downward while slowing in speed. 5. The elevator moves downward while increasing in speed.

4. The elevator moves downward while slowing in speed. When the elevator is moving downward, a downward acceleration would mean an increasing downward speed. Therefore, as your answer correctly states, an upward acceleration would mean a decreasing downward speed.

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? Ignore friction and air resistance. (Select all that apply.) 1. It will take less time to return to the point from which it was released. 2. It will stop well short of his face. 3. It will take more time to return to the point from which it was released. 4. It will smash his face. 5. Its mass will be greater.

1. It will take less time to return to the point from which it was released. The pendulum will swing back and forth more quickly (with a shorter period) because it is oscillating in a stronger gravitational field than that on Earth.

Why do the astronauts in the Space Shuttle float around? 1. The Space Shuttle is in free fall, so the shuttle and the astronauts inside it are continuously falling toward the Earth. They thus experience apparent weightlessness. 2. There is no gravity in the Space Shuttle because it is completely enclosed and shielded from the effects of gravity due to the Earth. 3. There is no gravity in the Space Shuttle because it is too far away from the center of the Earth.

1. The Space Shuttle is in free fall, so the shuttle and the astronauts inside it are continuously falling toward the Earth. They thus experience apparent weightlessness.

How do the high tides during a full moon compare to high tides during a new moon? 1. The high tides during a full moon are roughly the same as the high tides during a new moon. 2. The high tides during a full moon are higher than the high tides during a new moon. 3. The high tides during a full moon are not as high as the high tides during a new moon.

1. The high tides during a full moon are roughly the same as the high tides during a new moon. Tides during a full moon and a new moon are both spring tides. The tidal forces of the Sun and the tidal forces of the Moon are in the same direction for both cases.

When you lift twice the load twice as high, in half the time, the increase in potential energy is _______. 1. four times. 2. the same. 3. twice as much. 4. three times.

1. four times.

Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________. 1. greater than your normal weight at rest 2. equal to your normal weight at rest 3. less than your normal weight at rest

1. greater than your normal weight at rest Increasing speed means acceleration, and when the elevator is accelerating upward you will feel a force pressing you to the floor, making your weight greater than your normal (at rest) weight.

The constant G in Newton's equation _______. 1. makes the units of measurement consistent 2. shows gravity to be a relatively huge force 3. produces equilibrium 4. was measured by Newton

1. makes the units of measurement consistent

As the falling rocket plunges toward the event horizon, an observer in the orbiting rocket would see that the falling rocket __________. 1. slows down as it approaches the event horizon, and never actually crosses the event horizon 2. slows down near the event horizon so that it crosses the event horizon at a low speed 3. moves at constant speed as it approaches and crosses the event horizon 4. accelerates as it falls, and crosses the event horizon at high speed

1. slows down as it approaches the event horizon, and never actually crosses the event horizon Viewed from afar, time comes to a stop at the event horizon of a black hole, so falling objects never appear to cross the event horizon.

The Moon's gravitational pull is _________. 1. strongest on the side of Earth closest to the Moon 2. strongest on the side of Earth farthest from the Moon 3. the same on both sides of Earth

1. strongest on the side of Earth closest to the Moon Because the force of gravity is inversely proportional to the square of the distance from the Moon, it is strongest on the side of Earth that is closest to the Moon.

Recycled energy is mainly _______. 1. use of energy otherwise wasted 2. thermal energy 3. kinetic or potential energy. 4. energy that has been destroyed

1. use of energy otherwise wasted

One's weightlessness in space has most to do with _______. 1. rotational effects 2. one's mass 3. no support force 4. no gravity

3. no support force