# High School Physics : Understanding Universal Gravitation

## Example Questions

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### Example Question #1 : Understanding Universal Gravitation

Two satellites in space, each with a mass of , are  apart from each other. What is the force of gravity between them?

Explanation:

To solve this problem, use Newton's law of universal gravitation:

We are given the constant, as well as the satellite masses and distance (radius). Using these values we can solve for the force.

### Example Question #2 : Understanding Universal Gravitation

Two satellites in space, each with a mass of , are  apart from each other. What is the force of gravity between them?

Explanation:

To solve this problem, use Newton's law of universal gravitation:

We are given the constant, as well as the satellite masses and distance (radius). Using these values we can solve for the force.

### Example Question #1 : Understanding Universal Gravitation

Two satellites in space, each with equal mass, are  apart from each other. If the force of gravity between them is , what is the mass of each satellite?

Explanation:

To solve this problem, use Newton's law of universal gravitation:

We are given the value of the force, the distance (radius), and the gravitational constant. We are also told that the masses of the two satellites are equal. Since the masses are equal, we can reduce the numerator of the law of gravitation to a single variable.

Now we can use our give values to solve for the mass.

### Example Question #4 : Understanding Universal Gravitation

Two asteroids in space are in close proximity to each other. Each has a mass of . If they are  apart, what is the gravitational force between them?

Explanation:

To solve this problem, use Newton's law of universal gravitation:

We are given the constant, as well as the asteroid masses and distance (radius). Using these values we can solve for the force.

### Example Question #5 : Understanding Universal Gravitation

Two asteroids in space are in close proximity to each other. Each has a mass of . If they are  apart, what is the gravitational acceleration that they experience?

Explanation:

Given that , we already know the mass, but we need to find the force in order to solve for the acceleration.

To solve this problem, use Newton's law of universal gravitation:

We are given the constant, as well as the satellite masses and distance (radius). Using these values we can solve for the force.

Now we have values for both the mass and the force, allowing us to solve for the acceleration.

### Example Question #6 : Understanding Universal Gravitation

Two asteroids, one with a mass of  and the other with mass , are  apart. What is the gravitational force on the LARGER asteroid?

Explanation:

To solve this problem, use Newton's law of universal gravitation:

We are given the constant, as well as the asteroid masses and distance (radius). Using these values we can solve for the force.

It actually doesn't matter which asteroid we're looking at; the gravitational force will be the same. This makes sense because Newton's 3rd law states that the force one asteroid exerts on the other is equal in magnitude, but opposite in direction, to the force the other asteroid exerts on it.

### Example Question #6 : Understanding Universal Gravitation

Two asteroids, one with a mass of  and the other with mass  are  apart. What is the gravitational force on the SMALLER asteroid?

Explanation:

To solve this problem, use Newton's law of universal gravitation:

We are given the constant, as well as the asteroid masses and distance (radius). Using these values we can solve for the force.

It actually doesn't matter which asteroid we're looking at; the gravitational force will be the same. This makes sense because Newton's 3rd law states that the force one asteroid exerts on the other is equal in magnitude, but opposite in direction, to the force the other asteroid exerts on it.

### Example Question #7 : Understanding Universal Gravitation

Two asteroids, one with a mass of  and the other with mass  are  apart. What is the acceleration of the SMALLER asteroid?

Explanation:

Given that Newton's second law is , we can find the acceleration by first determining the force.

To find the gravitational force, use Newton's law of universal gravitation:

We are given the constant, as well as the asteroid masses and distance (radius). Using these values we can solve for the force.

We now have values for both the mass and the force. Using the original equation, we can now solve for the acceleration.

### Example Question #2 : Understanding Universal Gravitation

Two asteroids, one with a mass of  and the other with mass  are  apart. What is the acceleration of the LARGER asteroid?

Explanation:

Given that Newton's second law is , we can find the acceleration by first determining the force.

To find the gravitational force, use Newton's law of universal gravitation:

We are given the constant, as well as the asteroid masses and distance (radius). Using these values we can solve for the force.

We now have values for both the mass and the force. Using the original equation, we can now solve for the acceleration.

### Example Question #10 : Understanding Universal Gravitation

Two satellites are a distance  from each other in space. If one of the satellites has a mass of  and the other has a mass of , which one will have the smaller acceleration?

We need to know the value of the masses to solve

They will both have the same acceleration

Neither will have an acceleration

Explanation:

The formula for force and acceleration is Newton's 2nd law: . We know the mass, but first we need to find the force:

For this equation, use the law of universal gravitation:

We know from the first equation that a force is a mass times an acceleration. That means we can rearrange the equation for universal gravitation to look a bit more like that first equation:

can turn into:  and , respectively.

We know that the forces will be equal, so set these two equations equal to each other:

The problem tells us that

Let's say that  to simplify.

As you can see, the acceleration for  is twice the acceleration for . Therefore the mass  will have the smaller acceleration.

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