Physics Gravity + Inverse Square Law Quiz

What do m1 and m2 equal?

The masses of the two objects in question.

Formula for the gravitational force between any two objects:

F = (G * m1 *m2)/dsq

True or False: Gravity is one of the strongest forces in the universe.

FALSE. Gravity is the weakest force, the only reason it seems so powerful is because of the sheer size of astronomical bodies.

True or False: Astronauts are weightless due to the extreme lack of gravity on the ISS

False. They are weightless because the station itself is designed to be in a constant state of freefall. What this looks like in practice is that the ISS falls toward Earth and moves forward at about the same velocity. Because the two forces are equal, the astronauts are not pulled in a specific direction like they would be on Earth, so they float.

The mass of the Earth

6 x 10^24 kg

What does "G" in the universal law of gravitation equal

6.67 * 10 to the -11 power

Acceleration due to gravity

9.8 m/s/s

Define Weightlessness

Being without a support force.

Equation for G.

G = ((F/(M1*M2)/dsq))

How did Henry Kavendish calculate G?

He measured the tiny force between lead masses with a torsion balance.

Who first calculated G?

Henry Kavendish

List three applications of the Inverse Square Law NOT RELATED TO PHYSICS MATERIAL

How far paint spreads apart, the intensity of radiation, and the denseness of light on paper are all acceptable answers. But there are also several others.

How did Aristotle think celestial objects moved?

In divine circles via natural motion.

What happens to your weight as you move away from the Earth's center?

It decreases. Recall Weight is dependent on Gravity, and gravity is inversely proportional to the square of the distance between the two centers. As you increase your distance, you decrease the gravitational force and therefore decrease the weight.

If you double the distance between two objects, what happens to the gravitational force?

It is multiplied by scale factor of 1/dsq, so it is 1/4 the original force.

When solving for gravitational force, force always comes out in

Newtons

What allowed the mass of Earth to be calculated?

The calculation of the Gravitational Constant.

What does "dsquared" equal?

The distance between the CENTERS OF THE OBJECTS squared.

Why do you weigh more on an upward accelerating elevator?

The elevator floor (support force) is pushing harder against you to move you up so you, in turn, push harder against the ground. This means an increase in weight.

Inverse Square Law

The force of gravity is inversely proportional to the distance squared. (It's also applicable to several other things, but this is the application that matters for this quiz)

What did Newton reason when he saw the Apple fall? What do we call this?

The force that makes the apple fall to the Earth rather than stay on the tree is the same one that pulls all bodies in our universe away from the straight line they would follow if no other bodies were present. This is called the Newtonian Synthesis.

When is your weight measured in m * g?

When you're firmly supported and in equilibrium

Why are you weightless when you are without a support force?

Without a support force, you are not "pushing down" on anything so the FORCE of weight is not being utilized. When you stand on the floor (common support force), you are pushing down on it with your weight and, per Newton's third, it is pushing against you with the same force. When this is not happening and you are in freefall, THERE IS NO WEIGHT!