Chapter 16 Circular motion

Question 1

What is a radian?

Answer 1

It is the angle that is produced when an arc has a length that is equal to the radius of the circle

Question 2

How many radians are there in a circle?

Answer 2

There are 2π radians

Question 3

What is the equations to find the angle in radians?

Answer 3

Angle in radians = arc length / radius

Question 4

What is angular velocity?

Answer 4

It is the rate of change of the angle of an object rotating around a fixed point

Question 5

What is the symbol for angular velocity?

Answer 5

ω

Question 6

What is the equation to find angular velocity?

Answer 6

ω = θ / t
ω = angular velocity
θ = change of angle
t = change of time

Question 7

What are the units for angular velocity?

Answer 7

Radians per second (rad s^-1)

Question 8

How can the frequency of an object rotating around a point be calculated?

Answer 8

ω = 2πf

Question 9

What is a centripetal force?

Answer 9

It is a force that holds an object towards the centre of a circle.

Question 10

What angle does centripetal force act?

Answer 10

Always perpendicular to the direction of the movement of the object

Question 11

What is the equation for speed for a rotating object?

Answer 11

v = rω
v = SPEED
r = radius

Question 12

What is centripetal acceleration?

Answer 12

This is the acceleration towards the centre of the circle for a rotating object moving at a constant speed

Question 13

What are the equations for centripetal acceleration?

Answer 13

a = v^2 / r
a = ω^2r

Question 14

What is the equation for the centripetal force?

Answer 14

F = mv^2 / r
or
F = mω^2r

Question 15

How is the equation for the centripetal force derived?

Answer 15

By combining F = ma with a = v^2 / 2

Question 16

What is happening to the forces if the radius of a rotating object stays constant?

Answer 16

The centripetal force is equal to the force outward

Question 17

What are examples of centripetal force and what is causing the force?

Answer 17

Car turning - Friction
Swinging a ball on a string - Tension
Satellite rotating around the earth - Gravity

Question 18

How do banked surfaes work?

Answer 18

Normally on a flat surface, the centripetal force is just the friction. On a banked surface, the centripetal force is the friction and the normal contact force

Question 19

What are the properties of a fairground ride where a user stands and follows a vertical circular path?

Answer 19

The user feels lighter at the top of the rotation and heavier at the bottom of the rotation.