Question 1

Which of the following best describes the force that keeps a car moving in a circle on a flat road?

Accepted Answer

The frictional force between the tires and the road supplies the required centripetal force.

Question 2

For a car rounding a banked curve at the ideal speed, which force provides the entire centripetal force?

Accepted Answer

The horizontal component of the normal force.

Question 3

If a car is moving too fast on a banked curve and begins to skid outward, which type of friction is acting?

Accepted Answer

Kinetic friction, which is less effective than static friction.

Question 4

Which equation correctly expresses Newton’s Law of Universal Gravitation?

Accepted Answer

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

Question 5

A satellite orbits Earth in a circular path. What provides the centripetal force required for its motion?

Accepted Answer

The gravitational force between the Earth and the satellite.

Question 6

If the drag force on a falling object is proportional to its velocity, what is the terminal velocity $$v_t$$?

Accepted Answer

$$v_t = \frac{mg}{b}$$

Question 7

Which statement about the gravitational force between the Earth and the Moon is correct?

Accepted Answer

The Earth and Moon pull on each other with equal magnitude but opposite direction.

Question 8

What is the net gravitational force inside a thin spherical shell of uniform mass?

Accepted Answer

Zero

Question 9

Which of the following is true about static and kinetic friction?

Accepted Answer

Static friction can be larger than kinetic friction and can point toward the center of a circle during turning.

Question 10

A car is moving along a curved path at varying speed. What type of acceleration does it experience?

Accepted Answer

Both tangential and radial (centripetal) acceleration.

Question 11

If the net force on a car moving in a circle is not directed toward the center, what will happen?

Accepted Answer

The car will move in a path that is not circular, tending to go straight.

Question 12

Which of the following best describes the effect of banking a curve on a highway?

Accepted Answer

Banking allows the normal force to provide part or all of the required centripetal force, reducing reliance on friction.

Question 13

Which equation gives the centripetal acceleration $$a_c$$ for an object moving in a circle of radius $$r at $$speed $$v$$?

Accepted Answer

$$a_c = \frac{v^2$}{r}$$

Question 14

A skydiver reaches terminal velocity when:

Accepted Answer

The drag force equals the gravitational force.

Question 15

Which of the following is a consequence of Newton’s third law in gravitation?

Accepted Answer

You exert an upward gravitational force on the Earth equal in magnitude to the downward force the Earth exerts on you.

Question 16

If the radius of a banked curve is doubled but the speed of the car remains the same, what happens to the required centripetal force?

Accepted Answer

It is halved.

Question 17

Which of the following statements about the gravitational force between two masses is correct?

Accepted Answer

It is proportional to the product of the masses and inversely proportional to the square of the distance between them.

Question 18

A ball is whirled in a horizontal circle at constant speed. What is the direction of the net force acting on the ball?

Accepted Answer

Toward the center of the circle.

Question 19

If a car is moving on a banked curve at a speed lower than the ideal speed, what force helps prevent it from sliding down the bank?

Accepted Answer

Static friction acting up the bank.

Question 20

Which of the following is true about the gravitational force inside a spherically symmetric planet?

Accepted Answer

It acts as if all the mass interior to your position is concentrated at the center.

Circular Motion, Friction, and Newton’s Law of Universal Gravitation

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