Question 1

A point-like object moves along a circle of radius $$r. $$What is the formula for the circumference of the circle?

Accepted Answer

$$2\pi r$$

Question 2

The time it takes for an object to complete one revolution around a circle is called the period $$T. $$What is the formula for the average speed $$v of $$the object in terms of $$r$$ and $$T$$?

Accepted Answer

$$v = \dfrac{2\pi r}{T}$$

Question 3

In uniform circular motion, what is the direction of the instantaneous velocity of the object?

Accepted Answer

Tangent to the circle at every point

Question 4

Which of the following best describes the acceleration of an object in uniform circular motion?

Accepted Answer

It is always directed toward the center of the circle

Question 5

What is the formula for the magnitude of the centripetal acceleration $$a_c$$ for an object moving at speed $$v in a $$circle of radius $$r$$?

Accepted Answer

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

Question 6

A car of mass $$m$$ goes over the top of a frictionless hill of radius $$r. $$What is the maximum speed $$v_{crit}$$ the car can have at the top without losing contact with the road?

Accepted Answer

$$v_{crit} = \sqrt{g r}$$

Question 7

For a rollercoaster at the bottom of a loop, the normal force $$n is $$given by $$n = \dfrac{m v^2$}{r} + mg. $$Why do you feel heavier at the bottom?

Accepted Answer

Because the normal force is greater than your weight due to the required centripetal force

Question 8

A 1500 kg car is going around a flat curve of radius 100 m. If the coefficient of static friction between the tires and the road is 0.5, what is the maximum speed $$v_{max}$$ the car can have without slipping?

Accepted Answer

$$v_{max} = \sqrt{\mu_s g r}$$

Question 9

Which force is responsible for keeping the Earth in its orbit around the Sun?

Accepted Answer

Gravitational force

Question 10

When a ball is swung in a horizontal circle on a string, what provides the centripetal force?

Accepted Answer

Tension in the string

Question 11

A car is going around a banked curve with no friction. What force provides the necessary centripetal force?

Accepted Answer

The horizontal component of the normal force

Question 12

At what point in the motion of a playground swing is the tension in the chains greatest?

Accepted Answer

At the lowest point of the swing

Question 13

If the magnitude of the tangential velocity of an object in circular motion stays constant, what type of motion is this?

Accepted Answer

Uniform circular motion

Question 14

Which of the following is true about the centripetal force in circular motion?

Accepted Answer

It is the net force directed toward the center of the circle

Question 15

A rollercoaster goes over the top of a loop. At the top, the normal force $$n is $$given by $$n = \dfrac{m v^2$}{r} - mg. $$What happens if $$n$$ becomes zero?

Accepted Answer

The rollercoaster is just about to lose contact with the track

Question 16

Which of the following real-world scenarios is an example of uniform circular motion?

Accepted Answer

A satellite orbiting Earth at constant speed

Question 17

If the period $$T of an $$object in circular motion doubles, what happens to its average speed $$v ($$assuming the radius $$r$$ stays the same)?

Accepted Answer

It is halved

Question 18

A car of mass $$m is $$going around a flat curve of radius $$r at $$speed $$v. $$What is the minimum coefficient of static friction $$\mu_s$$ required to prevent slipping?

Accepted Answer

$$\mu_s = \dfrac{v^2$}{g r}$$

Question 19

Which of the following statements about centripetal acceleration is correct?

Accepted Answer

It is always perpendicular to the instantaneous velocity

Rotational Motion and Uniform Circular Motion: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard