Unit 6 Periodic Motion

Question 1

What is the period?

Answer 1

Time taken to complete one rotation in seconds.

Question 2

What is frequency?

Answer 2

The number of revolutions per second in Hz.

Question 3

What is angular speed?

Answer 3

The angle turned through per second in rads^-1.

Question 4

If an object is in uniform circular motion, what conclusions can you draw from the object?

Answer 4

The object has a constant linear speed but a constantly changing velocity due to the object continuously changing direction. Therefore the object must be accelerating.

Question 5

If an object is accelerating and is in uniform circular motion, what is this acceleration called and where is it directed towards?

Answer 5

This acceleration is called the centripetal (acts towards the centre of the circular path) acceleration and is perpendicular to the direction of the linear speed.

Question 6

What is centripetal acceleration caused by?

Answer 6

Caused by a centripetal force of constant magnitude that also acts perpendicular to the direction of motion (towards the centre) so the centripetal acceleration and force acts in the same direction.

Question 7

What is angular speed (⍵) of a body in circular motion is defined as?

Answer 7

The rate of change in angular displacement with respect to time is measured in rad s^-1.

Question 8

How can you calculate angular speed (⍵) of a body ?

Answer 8

⍵ = Δθ/Δt where Δθ is the change in angular displacement.

Question 9

What is centripetal acceleration defined as?

Answer 9

The acceleration of an object towards the centre of a circle when an object is in motion (rotating) around a circle at a constant speed.

Question 10

If an object is moving in a circle, is it moving in equilibrium?

Answer 10

No, it is not moving in equilibrium, as it has a resultant force acting upon the object which is known as the centripetal force and is what keeps the object moving in a circle.

Question 11

What is centripetal force defined as?

Answer 11

The resultant force towards the centre of the circle required to keep a body in uniform circular motion. It is always directed towards the centre of the body’s rotation.

Question 12

For a vehicle going over a hill, what is its centripetal force?

Answer 12

For a vehicle going over a hill, what is its centripetal force?

Question 13

What is the maximum speed at which a vehicle can stay in contact with the road?

Answer 13

V = sqrt(gr)

Question 14

For a vehicle on a banked track, what is its centripetal force?

Answer 14

mv^2/r = Nsin(theta)

Question 15

What is the velocity of a vehicle on a banked track?

Answer 15

v^2 = grtan(theta)

Question 16

What is simple harmonic motion?

Answer 16

A specific type of oscillation.

Question 17

What are the conditions for simple harmonic motion?

Answer 17

The acceleration is proportional to the displacement
The acceleration is in the opposite direction to the displacement

Question 18

What is the maximum angle a simple pendulum can make with the vertical if it is to be in SMH?

Answer 18

10 degrees

Question 19

Define damping

Answer 19

Process by which an oscillating object loses energy to its surrounding, which are caused by damping forces such as air resistance which decrease the amplitude of the oscillation over time

Question 20

What is light damping?

Answer 20

This involves a small damping force, leading to a gradual decrease in amplitude

Question 21

What is critical damping?

Answer 21

Causes the oscillation to stop in the shortest possible time, returning the object to its equilibrium position without overshooting it.

Question 22

What is heavy damping?

Answer 22

Causes the objects to return to its equilibrium position without oscillating.

Question 23

Define a free vibration

Answer 23

Oscillation that occurs with no transfer of energy to or from the surroundings

Question 24

What are the only forces acting on a freely oscillating object?

Answer 24

Forces providing the resultant restoring force

Question 25

What is a forced vibration?

Answer 25

Oscillation where a periodic external driving force is applied

Question 26

State the natural frequency of an object

Answer 26

Frequency at which it would vibrate if left to vibrate freely with no damping or driving forces acting on it

Question 27

Define resonance

Answer 27

Process by which a maximum in the amplitude of a forced oscillation is produced. Resonance, occurs when the driving frequency = natural frequency of an object

Question 28

What is the displacement time graph for SMH?

Answer 28

Cosine graph

Question 29

What is the velocity time graph for SMH?

Answer 29

-sine graph

Question 30

What is the acceleration time graph for SMH?

Answer 30

-cosine graph

Question 31

State the restoring force for a spring with spring constant k stretched by displacement x.

Answer 31

F = -kx