Question 1

In the context of uniform circular motion, what is the direction of the force of gravity acting on the Earth as it orbits the Sun?

Accepted Answer

Radially inward, toward the Sun

Question 2

According to Newton’s 1st law of motion, what happens to the Earth’s motion if the force of gravity from the Sun is suddenly turned off?

Accepted Answer

The Earth will continue in a straight line tangent to its orbit

Question 3

Which equation correctly represents the gravitational force between two masses $$m_1$$ and $$m_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = \frac{G m_1$ m_2$}{r^2$}$$

Question 4

If the radius of a moon’s orbit around Earth is increased from 2 units to 3 units, what happens to the magnitude of the gravitational force between the Earth and the moon?

Accepted Answer

It decreases by a factor of $$\frac{4}{9}$$

Question 5

What must be adjusted to keep the moon in a circular orbit when its orbital radius is increased?

Accepted Answer

Decrease the moon’s velocity

Question 6

Which equation gives the orbital velocity $$v$$ for a body of mass $$m in a $$circular orbit of radius $$r$$ around a mass $$M$$?

Accepted Answer

$$v = \sqrt{\frac{G M}{r}}$$

Question 7

If the moon is moved to a location only 1 unit away from Earth, what happens to the force of gravity acting on the moon?

Accepted Answer

It increases by a factor of 4

Question 8

What happens to the velocity required for the moon to stay in a circular orbit as the radius decreases?

Accepted Answer

The required velocity increases

Question 9

A satellite is in a stable circular orbit around Earth. If its velocity is suddenly increased, what will happen to its orbit?

Accepted Answer

It will move to a larger, elliptical orbit

Question 10

Which of the following best describes the path of the moon if gravity is turned off while it is in orbit around Earth?

Accepted Answer

It will move in a straight line tangent to its orbit

Question 11

If the moon is placed at a larger radius but its velocity is not adjusted, what is the most likely outcome?

Accepted Answer

The moon will move in an elliptical orbit

Question 12

Which law explains why the Earth continues moving in a straight line when gravity is turned off?

Accepted Answer

Newton’s 1st law of motion

Question 13

If the moon’s orbital radius is halved, by what factor does the gravitational force change?

Accepted Answer

It increases by a factor of 4

Question 14

Which of the following is a real-world consequence of Newton’s laws for planetary motion?

Accepted Answer

Planets move in straight lines unless acted upon by a force

Question 15

A spacecraft is orbiting Earth at radius $$r. If it $$wants to move to a higher orbit, what must it do?

Accepted Answer

Increase its velocity

Question 16

Which of the following best describes the relationship between orbital radius and orbital velocity for a circular orbit?

Accepted Answer

As radius increases, velocity decreases

Question 17

If a planet’s orbital radius is doubled, what happens to its orbital velocity?

Accepted Answer

It decreases by a factor of $$\sqrt{2}$$

Question 18

Which equation represents the centripetal force required for uniform circular motion?

Accepted Answer

$$F = \frac{m v^2$}{r}$$

Question 19

What is the primary reason the moon does not fall directly toward Earth?

Accepted Answer

Its tangential velocity keeps it in orbit

Question 20

Which of the following best describes the effect of gravity on the path of a planet in orbit?

Accepted Answer

Gravity acts as a centripetal force, keeping the planet in orbit

Gravity and Circular Orbits: Forces, Motion, and Orbital Dynamics

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