universal gravitation quiz (11/24)

For some massive stars, gravitational collapse doesn't stop until the density of the star becomes so enormous that even light cannot escape. Such a star becomes a black hole. (T/F)

true

Newton's formulation of the universal law of gravitation influenced society because other scientists, artists, writers, and philosophers of the 1700s began to hope that whole universe might be described by equally simple and universal laws. (T/F)

true

The component of an orbiting satellite's velocity that is parallel to Earth's surface is its tangential velocity. (T/F)

true

The force on a ball decreases as the ball moves farther from Earth. (T/F)

true

There is a force on Earth that is directed toward the sun. (T/F)

true

A planet has half the mass of the Earth and half the radius. Compared to its weight on Earth, an apple on this planet would weigh _____.

twice as much

If a weight scale shows that you weigh 200 kg on the surface of the Earth, and then you skydive with both of your feet attached to the scale, you will read a weight of

0 kg

Suppose the gravitational force between two spheres is 30 N. If the magnitude of each mass doubles, what is the force between the masses?

120 N

A 560-N woman stands on top of a very tall ladder so she is one Earth radius above Earth's surface. How much does she weigh?

140 N

The force of gravity acting on you will increase if you _____.

stand on a planet with a radius that is shrinking

Suppose the gravitational force between two massive spheres is 100 N. If the distance between the spheres is doubled, what is the force between the masses?

25 N

Suppose the gravitational force between two spheres is 70 N. If the distance between the spheres is halved, what is the force between the masses?

280 N

Suppose the gravitational force between two masses is 70 N. If the magnitude of one of the masses halves, what is the force between the masses?

35 N

Since Earth is attracted to the sun, why doesn't it fall into the sun?

Because it has sufficient tangential velocity

Why did Newton think there was a force acting on the moon?

Because the moon moves in a curved path

If you stand on a weight scale in an elevator that is accelerating upwards, why do you observe an increase in your weight?

Because you are accelerating upwards, there is more compression of the springs of the scale. The weight reading on the scale reflects the amount of compression of the springs.

By noticing that Uranus's orbit is perturbed and by using the law of gravitation, two astronomers independently discovered _____.

Neptune

Newton hypothesized that the moon _____.

all of the above

The gravitational force between two massive spheres

all of the above

Gravitational forces are the weakest forces found in nature. Because of this _____.

gravitational forces that are easily observed involve one or more large masses

A very massive object A and a less massive object B move toward each other under the influence of mutual gravitation. Which force, if either, is greater?

both forces are the same

If Earth's mass decreased to one half its original mass, with no change in radius, then your weight would _____.

decrease to one half your original weight

A supplier wants to make a profit by buying metal by weight at one altitude and selling it at the same price per pound at another altitude. The supplier should _____.

disregard altitude because it has a negligible effect

One way that astronomers detect planets around distant stars is by observing to see if there is a _________ in the light that reaches us from a particular star. The reason that the star moves away or toward us is a ________ due to the gravitational effects of the planet.

doppler shift; perturbation

Which is greater, the gravitational force between Earth and the moon, or the force between Earth and the sun?

earth-sun

Because Earth and moon are gravitationally attracted toward each other, they will soon collide (T/F)

false

Because Earth is "falling" around the sun, it will eventually crash into it.

false

If Earth were its present size but twice as massive, we would weigh less.

false

If Earth were to disappear, the moon would still orbit the place where Earth was.

false

The condition of weightlessness is the absence of gravity. (T/F)

false

The force of attraction between two masses depends inversely on the square of the distance between the masses. Any law that has this kind of dependence on distance is called an inverse distance law. (T/F)

false

The gravitational force of Earth on an object does not depend upon the object's mass. (T/F)

false

Newton had the insight to see that the _____.

force on the moon has the same nature as the force on an apple

If the radius of Earth decreased, with no change in mass, your weight would _____.

increase

If the mass of Earth increased, with no change in radius, your weight would _____.

increase also

Two objects move toward each other because of gravitational attraction. As the objects get closer and closer, the force between them _____.

increases

The force of gravity on you is greatest when you are standing _____.

just above Earth's surface

Jupiter has more than 300 times the mass of Earth. Yet on Jupiter's surface an object weighs only about 3 times as much as it would on Earth. The explanation to this involves Jupiter's _____.

large radius

A lunar month is about 28 days. If the moon were closer to Earth than it is now, the lunar month would be _____.

less than 28 days

If you were to weigh yourself in an elevator that is accelerating upward, compared to your ordinary weight you would weigh _____.

more

A hollow spherical planet is inhabited by people who live inside it, where the gravitational field is zero. When a very massive space ship lands on the planet's surface, the gravitational field inside the planet is _____.

nonzero, directed toward the spaceship

There are two main processes going on in the sun that keep the sun in existence. These processes are gravitation and _____.

nuclear fusion

If you drop a stone into a hole drilled all the way to the other side of Earth, the stone will _____.

speed up until it gets to the center of Earth

The force of gravity on you is greatest when you are standing _____.

on Earth's surface

Consider the gravitational force between Earth and a meteor in outer space. If the meteor moves so its distance from the Earth's center doubles, the gravitational force on the meteor will be _____.

one quarter

If you stood atop a ladder on Earth that was as tall as Earth's radius (so you were twice as far from Earth's center) your weight atop the ladder would be _____.

one quarter its normal value

If the sun were to collapse to form a black hole (quite unlikely), Earth would _____.

orbit the black hole just as it orbits the sun now

Newton reasoned that the gravitational attraction between Earth and the moon must be _____.

reduced by distance

When a star collapses to form a black hole, its mass _____.

remains the same

Compared to the gravitational field on the surface of Earth, the gravitational field well below Earth's surface is _____.

smaller

Each of us weighs a tiny bit less on the ground floor of a skyscraper than we do on the top floor. One reason for this is that _____.

the mass of the building attracts you upward slightly

The reason the moon does not fall into Earth is that _____.

the moon has a sufficiently large orbital speed

If you were to weigh yourself in an elevator that is in free fall, compared to your ordinary weight, you would weigh _____.

zero

The gravitational field strength at the center of Earth is _____.

zero