Chapter 9: Gravity

Question 1

Any particle of matter in the universe attracts any other with a force of varying directly as a product of the masses and inversely as the square of the distance between them.

Answer 1

The law of universal gravitation

Question 2

According to the equation for gravitational force, what happens to the force between two bodies if the mass of one of the bodies is doubled? If both masses are doubled?

Answer 2

When one mass is doubled, the force between it and the other mask doubles. If both masses „ the force is a four times as great.

Question 3

The moon falls around the earth rather than straight into it. If the moons tangential velocity or zero, how would it move?

Answer 3

The moon would fall straight down and crash into the earth

Question 4

Gravitational force acts on our bodies in proportion to their masses. Why then doesn’t a heavy body fall faster than light body?

Answer 4

A feather and a coin dropped in a vacuum have equal acceleration‘s because both have the same weight/mass. Likewise for all heavy and light falling bodies. G is constant when air resistance isn’t a factor. 

Question 5

Name the following equation.

Answer 5

The universal law of gravitation.

Question 6

Intensity equals the inverse of the square of the distance from the source.

Answer 6

Inverse Square Law

Question 7

By how much does the gravitational force between two objects decrease when the distance between their centers is doubled? Tripled? Increase tenfold?

Answer 7

The force decreases to 1/4, 1/9, and 1/100 of the original value.

Question 8

The gravitational force on an apple at earths surface is 1 N. What was the force be if the Apple were raised to an altitude matched earths radius?

Answer 8

Raised by one earth radius means that the apples twice earths radius from earths center by the inverse square law, twice the distance means 1/4 the force; 1/4 equals .25 N.

Question 9

Consider an apple at the top of a tree that is pulled by earths gravity with a force of 1 N. If the tree is twice as tall will the force of gravity be 1/4 is strong?

Answer 9

no, because an apple at the top of the twice as tall apple tree is not twice as far from earth’s center. the taller apple tree would need a height equal to earths radius for the apples weight at its top to reduced to 1/4 N. Before its weight decreases by 1%, an apple or any object must be raised 32 km – nearly 4 times the height of Mount Everest.

Question 10

The force of gravity, like any force, can produce…

Answer 10

Acceleration

Question 11

The pressing against earth is the sensation we interpret as…

Answer 11

weight

Question 12

If an elevator accelerates upward, the bathroom scale and floor push harder against your feet. So spring compression inside the scale is greater. The scale will show…

Answer 12

an increase in my weight

Question 13

If an elevator accelerates downward, in the bathroom scale and floor do not push as hard against your feet. The scale will show…

Answer 13

a decrease in weight

Question 14

Objects under the influence of gravity accelerate…

Answer 14

toward eachother

Question 15

The force of gravity, like any force, can produce

Answer 15

acceleration

Question 16

Most often, the force exerted by gravity on an object. More generally, the force as read on a weighing scale that an object exerts on a supporting service or other means of support.

Answer 16

weight

Question 17

The condition in which an object experience has no support force, such as one in freefall or an orbit.

Answer 17

weightless

Question 18

If an elevator is in freefall, the support force and the reading on a weighing scale are…

Answer 18

zero

Question 19

Gravity is not felt as weight when there is no…

Answer 19

support force

Question 20

In what sense is drifting in space far away from all celestial bodies like stepping down off the stepladder?

Answer 20

In both cases, you experience weightlessness. Drifting in deep space, you remain way less because no discernible force acts on you. Stepping from a step ladder, you are only momentarily weightless because of a momentary lapse of support force.

Question 21

True or false? In addition to no support force, inhabitants of the ISS are weightless because they are beyond the main pull of earths gravity.

Answer 21

False. The pull of earths gravity at the altitude of the ISS is about 90% as strong as at earths surface. That’s why it hugs earth and it doesn’t fly off into space. The experience of floating is due to the absence of a support force.

Question 22

Oh for sale that exist in the space around every mass or group of masses; Measured in newtons per kilogram.

Answer 22

Gravitational field