Physics test 8th grade #3

Question 1

What two effects does a planet’s gravity have on the spacecraft ?

Answer 1

It can change its path and speed it up

Question 2

What two questions did Newton try to answer?

Answer 2

What keeps Earth and the moon in orbit?
Why don’t they just fly into space?

Question 3

What did Newton decide was the answer to his questions?

Answer 3

He decided that there was a force acting between the Earth and the Moon, keeping them in orbit.

Question 4

How did Newton connect the apple and the Moon?

Answer 4

Newton realized that the force that pulls an apple to the ground might be the same force pulling the moon towards Earth

Question 5

Give Newton’s universal law:

Answer 5

Newton’s universal law states that every object in the universe attracts every other object.

Question 6

What two factors affect the strength of the force? (key concept)

Answer 6

The two factors that affect the strength of the force are the masses of the objects and the distance between them.

Question 7

What does the strength of gravity depend upon?

Answer 7

The strength of gravity depends on the masses of each object

Question 8

What is mass?

Answer 8

Mass is the amount of matter in an object

Question 9

Which exerts a greater attraction on you, the Earth or the table? Give a reason.

Answer 9

Earth exerts a greater attraction than the table does because it has a much greater mass than the table does. Therefore it exerts more force.

Question 10

What is weight?

Answer 10

Weight is the measure of the force of gravity of an object

Question 11

Why can weight change?

Answer 11

Weight can change depending on its location (some locations have less mass and therefore exert less force) and also depending on the strength of the gravity

Question 12

Why do you weigh less on the Moon?

Answer 12

You weigh less on the moon because the moon has less mass than the Earth therefore the pull of gravity is also less.

Question 13

Is going to the Moon the same as going on a diet? Explain

Answer 13

No, your mass does not change when you go to the moon but it does if you go on a diet. The only reason why you weigh less on the moon is because there is less gravity acting upon you, not because you have less mass.

Question 14

How does distance affect the force of gravity between two objects?

Answer 14

The more distance between two objects, the less gravity affects that object. The force of gravity decreases as distance increases

Question 15

If the distance between two objects is doubled what happens to the force?

Answer 15

If the distance between two objects doubled, the force would decrease to one fourth of its original value.

Question 16

If the original force is 81 N, what is the force at
double the distance?

Answer 16

81 / 4 = 20.25

Question 17

If the original force is 81 N, what is the force at triple the distance?

Answer 17

81 / 9 = 9

Question 18

What evidence is there that another factor besides gravity is involved in the motion of bodies?
(Be careful it is not about something happening )

Answer 18

Because the earth does not crash into the sun and the moon does not crash into the earth, it means that there is another force, not only gravity. If there was only gravity, the collisions previously mentioned would happen.

Question 19

What is inertia described as? Give an example

Answer 19

Inertia is the tendency of an object to resist a change in motion. That an object in motion will remain in motion unless another force acts upon it. For example, when a car brakes suddenly and you are thrown against your seatbelt.

Question 20

Give another example of a situation that involves inertia, explain how it shows inertia.

Answer 20

Another example would be hitting a carpet that is dirty. When the carpet is hit, it is moved suddenly and the dirt particles are left in the same position. Eventually they fall to the ground because of gravity, but it is inertia that makes the dirt particles resist the change of motion.

Question 21

How does Newton turn the idea of inertia into a law ? Try to explain

Answer 21

Newton turned the idea of inertia into a law by saying that an object will not change its motion or (lack thereof) unless another force acts upon it.This is the same as inertia because inertia is the resistance of change and this law describes it with examples.

Question 22

What two factors combine to keep the Earth in orbit around the Sun ? (key concept)

Answer 22

The two factors that keep the earth in orbit are a combination of inertia and gravity

Question 23

What stops the Moon traveling in a straight line?

Answer 23

Earth’s gravity stops the moon from traveling in a straight line

Question 24

What stops the Moon crashing into the Earth?

Answer 24

The inertia of the moon

Question 25

What would happen to the Moon if the Earth’s mass suddenly increased? Try to give a reason using the two answers above.

Answer 25

The Moon will: move closer to the earth and eventually crash into it
Because: As mass increases so does the force of attraction.