Circular Motion

Question 1

What is angular velocity

Answer 1

The Angular Velocity is the Angle an Object Rotates Through per Second

Question 2

What is the equation for angular velocity

Answer 2

ω= θ/t

w is angular velocity measured in radians per second

Question 3

What is the equation linking linear and angular velocity

Answer 3

V= rω

Where v is linear velocity (ms^-1)
r is the radius of the circle (m)
ω angular velocity (rads^-1)

Question 4

What is frequency

Answer 4

Frequency is the number of complete revolution per second (revs^-1 or hertz)

Question 5

What is period

Answer 5

The time taken (in seconds) for a complete revolution

Question 6

What is the equation linking frequency and period

Answer 6

f=1/T

Question 7

What is the equation for angular velocity involving frequency and period

Answer 7

ω=2pi/T

ω =2pif

Question 8

What is the equation for angular velocity involving frequency and period

Answer 8

ω=2pi/T

ω =2pif

Question 9

Why is a car going at a constant speed around a roundabout at a constant speed said to be accelerating

Answer 9

It velocity is changing because it direction is changing.
Since acceleration is defined as the rate of change in velocity over time the car is accelerating even though it isn’t going any faster.

Question 10

What is the acceleration of an object going in circle called, and where is it directed to

Answer 10

Centripetal acceleration and it is always directed to the cente of the circle

Question 11

What is the formula to calculate centripetal acceleration

Answer 11

a=v^2/r and a= ω^2 r

V is linear velocity

ω is angular velocity in rad s^-1

r = radius in m

Question 12

What law explains why there must be a centripetal force

Answer 12

Newtons 1st law (if an object is accelerating there must be a net force acting on it)

Question 13

What is the force that allows an object to travel in a circular path

Answer 13

An object will travel in a circular path if there is a net force acting on it perpendicular to the velocity. This is called centripetal force and it always act towards the centre of the circle.

Question 14

What are the equations to calculate centripetal force and why do these make sense

Answer 14

Since F=ma

F=mv^2/r

F=m ω^2 r

Question 15

What would happen if the centripetal force stopped being applied

Answer 15

The object would fly off at a tangent

Question 16

What happen to the kentic energy as the object spins round

Answer 16

Although the force changes direction, the objects velocity remains perpendicular to the direction of the force. The object never moves towards or away from the centre of the circle, so there is now motion in the direction of the force. Hence no work is done on the object, and therefore the kinetic energy (and therefore speed remain constant)

Question 17

In simple harmonic motion, what does displacement refer to

Answer 17

The distance of the object from the midpoint (which the object is oscillating about)

Question 18

Describe the movement of an object moving with similar harmonic motion, with example

Answer 18

An object moving with simple harmonic motion (SHM)
Midpoint
oscillates to and fro, either side of a midpoint.
Pendulums and mass-spring systems (e.g. a mass hanging on a spring that’s free to move up and down) are two examples.

Question 19

State the condition needed for movement to be simple harmonic

Answer 19

Condition for SHM: an oscillation in which the acceleration of an object is directly proportional to its displacement from the midpoint, and is directed towards the midpoint.

Question 20

Describe the resultant force on an object in moving in simpler harmonic motion

Answer 20

There is always a restoring force pulling or pushing the object back towards the midpoint.
The size of the restoring force depends on the displacement, and the force makes the object accelerate towards the midpoint.