Ch. 09 Homework

What is the magnitude of Earth's gravitational force on a 1-kg body at Earth's surface? A. 1 kg B. 10 N C. 6.67 × 10 -11 N D. 6.67 × 10 -11 kg

B. 10 N

If Earth shrank with no change in its mass, what would happen to your weight at the surface? A. It would stay the same. B. It would decrease. C. It would increase. D. It would decrease at first and then increase.

C. It would increase.

When you weigh yourself on a bathroom scale in an elevator accelerating upward, are the springs in the scale more, or less, compressed? Accelerating downward? A. Less compressed while accelerating upward, but more compressed while accelerating downward. B. Less compressed while accelerating upward and while accelerating downward. C. More compressed while accelerating upward, but less compressed while accelerating downward. D. More compressed while accelerating upward and while accelerating downward.

C. More compressed while accelerating upward, but less compressed while accelerating downward

Why do both the Sun and the Moon exert a greater gravitational force on one side of Earth than the other side? A. The Sun exerts a stronger force on the side of Earth furthest from the Sun, and the Moon exerts a stronger force on the side nearest the Moon. B. The Sun exerts a stronger force on the side of Earth furthest from the Sun, and the Moon exerts a stronger force on the side furthest from the Moon. C. The Sun exerts a stronger force on the side of Earth nearest the Sun, and the Moon exerts a stronger force on the side nearest the Moon. D. The Sun exerts a stronger force on the side of Earth nearest the Sun, and the Moon exerts a stronger force on the side furthest from the Moon.

C. The Sun exerts a stronger force on the side of Earth nearest the Sun, and the Moon exerts a stronger force on the side nearest the Moon.

Why is a black hole invisible? A. A black hole is a black dwarf star. B. A black hole is made of matter that absorbs all wavelengths of light. C. The escape velocity of the black hole is greater than the speed of light. D. A black hole is surrounded by an opaque cloud of dust.

C. The escape velocity of the black hole is greater than the speed of light.

Where do you weigh more--at the bottom of Death Valley or atop one of the peaks of the Sierra Nevada? Defend your answer. A. You weigh more on the summit because the air buoys you up less. B. You weigh more on the summit, because the higher you go, the harder you fall. C. You weigh more in Death Valley because you are closer to the center of Earth. D. You weigh more in Death Valley because more atmosphere pushes down on you.

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

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

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

How does the Moon "fall" without getting closer to us? A. It falls away from the straight path that it would follow if there were no forces acting on it. B. The Moon "falls" toward Earth a bit on every orbit. C. The Moon "falls" away from Earth a bit on every orbit. D. The Moon does not "fall." Instead, it moves in a circle at a constant radius.

A. It falls away from the straight path that it would follow if there were no forces acting on it.

Which has the higher tides: spring tides or neap tides? Why? A. Spring tides are higher, because the tides from the Moon and Sun add together. B. Spring tides are higher, because the tides from the Moon and Sun partially cancel. C. Neap tides are higher, because the tides from the Moon and Sun add together. D. Neap tides are higher, because the tides from the Moon and Sun partially cancel.

A. Spring tides are higher, because the tides from the Moon and Sun add together.

What happens to the force of attraction between two planets when the distance between them is doubled? A. The force decreases to one quarter. B. The force doubles. C. The force decreases to half. D. The force remains the same.

A. The force decreases to one quarter.

When you weigh yourself on a bathroom scale in an elevator moving upward at constant velocity, are the springs in the scale more, or less, compressed? Moving downward at constant velocity? A. There would be no more compression and no more expansion for both upward and downward motion. B. Less compressed while moving upward and more compressed while moving downward. C. More compressed while moving upward and while moving downward. D. More compressed while moving upward and less compressed while moving downward.

A. There would be no more compression and no more expansion for both upward and downward motion.

Why are occupants of the International Space Station weightless? A. They are in free fall. B. Centripetal force cancels gravity in the space station. C. They are so far from Earth that gravity is essentially zero. D. The floor of the space station is made from cavorite, which blocks gravity.

A. They are in free fall.

Do tides occur in the Earth's interior? A. Yes, due to the difference in gravitational force across the core. B. No, due to the difference in gravitational force across the core. C. No, due to the strength of the gravitational force at the center of the core. D. Yes, due to the strength of the gravitational force at the center of the core.

A. Yes, due to the difference in gravitational force across the core.

When is your weight measured as mg? A. For a mass near the surface of Earth in free fall B. For a non-accelerating mass near the surface of Earth C. For a mass accelerating upward with an acceleration g near the surface of Earth D. For a mass accelerating downward with an acceleration g

B. For a non-accelerating mass near the surface of Earth

What happens to the strength of the gravitational field at the surface of a star that shrinks? A. It first increases and then it decreases. B. It increases. C. It decreases. D. It stays the same.

B. It increases.

How does the force of gravity between two bodies change when the distance between them is halved? A. The force is cut in half. B. The force quadruples. C. The force decreases to ¼ of its initial value. D. The force doubles.

B. The force quadruples.

What happens to the force of attraction between two planets when the masses of both are doubled? A. The force remains the same. B. The force quadruples. C. The force doubles. D. The force increases by 16.

B. The force quadruples.

Earth's gravitational field is strongest at _______. A. Earth's center B. infinity, in principle C. Earth's surface D. either the Earth's center or at its surface

C. Earth's surface

What did Newton discover about gravity that was not known at the time? A. The equation for the force of gravity. B. The law of universal gravitation. C. The Newtonian synthesis. D. All of the above.

D. All of the above.