Chapter 13 Test

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.

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

On Earth's surface.

The gravitational force between two massive spheres

All of the above. (Is always an attraction, depends on how massive they are, depends inversely on the square of the distances between them.)

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

Increase also.

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

Increase.

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

Increases.

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.

The force of gravity acting on you will increase if you standing ______.

Stand on a planet with a radius that is shrinking.

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

25 N.

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 of its original mass, with no change in radius, then your weight would ______.

Decrease to one half your original weight.

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

Earth-Sun.

61.7 cm mark

Explanation: The force is a function of the mass and the distance from the balance point (center of mass). So, with a 10.0N mass at the 15.0 cm mark, it is (50-15) = 35 cm from one side of the balance point. Thus, a 30.0N mass must be placed: 10 N 30 N ⋅ 35 c m = 11.7 cm on the other side of the balance point - the (50 + 11.7) = 61.7 cm mark.

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

Gravitational forces that are easily observed involve one or more large masses.

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.

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's has a sufficiently large orbital speed.

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.