13 Oscillations

Question 1

Amplitude

Answer 1

Max displacement of a particle from the equilibrium

Question 2

Frequency

Answer 2

Number of oscillations per second

Question 3

Time period

Answer 3

Time taken to complete one oscillation

Question 4

Equations for time period

Answer 4

T = 1/f

T = 2pi/angular speed

Question 5

Simple harmonic motion

Answer 5

The oscillatory motion about an equilibrium position such that the acceleration is proportional to the displacement and always directed towards the equilibrium position

Question 6

What equation is simple harmonic motion defined by

Answer 6

a = -w^2 x X

Question 7

How could a displacement time graph be found using an experiment

Answer 7

The transmitter of a displacement sensor could be attached to a mass on a spring which oscillates

Question 8

What is the equation for the SHM displacement graph

Answer 8

X = A x cos(wt)

Question 9

Equation for SHM velocity graph

Answer 9

V =-A x w x sin(wt)

Question 10

Equation for SHM acceleration graph

Answer 10

a = -A x w^2 x cos(wt)

Question 11

What is the maximum displacing equal to?

Answer 11

Amplitude

Question 12

What is the maximum velocity equal to?

Answer 12

A x w

Question 13

What is the maximum acceleration equal to?

Answer 13

A x w^2

Question 14

Equation for mass on spring

Answer 14

F = -kx

F= force
k= stiffness/ spring constant
x= displacement

Question 15

Mechanical oscillator equation linking time period, mass and spring constant

Answer 15

T =2pi x route(m/k)

Question 16

Equation for pendulum linking time period, length and gravity

Answer 16

T= 2pi x route(l/g)

Question 17

For what angles does a pendulum display simple harmonic motion

Answer 17

Less than 10° to the vertical

Question 18

What is true of the time period of a heavy mass on a weak spring?

Answer 18

It’s large

Question 19

What are the two main forms of energy in simple harmonic oscillators?

Answer 19

KE and PE

Question 20

Equation for kinetic energy (learn)

Answer 20

KE = 1/2mv^2

KE = 1/2m x A^2 x w^2 x sin^2(wt)

Question 21

Equation for potential energy (learn)

Answer 21

PE= 1/2kx^2

PE= 1/2m x A^2 x w^2 x cos^2(wt)

Question 22

Equation for total energy (learn)

Answer 22

E total= PE + KE

E total= 1/2m x A^2 x w^2

Question 23

Free oscillations

Answer 23

When no energy is lost from an oscillator so the motion would continue would continue forever

Question 24

Damped oscillation

Answer 24

When energy is transferred out of the system

Question 25

Forced oscillations

Answer 25

When a system is made to vibrate at the frequency of an external driving force

Question 26

How does the amplitude of an oscillation change with light damping?

Answer 26

The amplitude decreases exponentially over time

Question 27

Example of a system with light damping

Answer 27

Pendulum oscillating in air

Question 28

How does the amplitude of an oscillation change with heavy damping?

Answer 28

The amplitude returns to the equilibrium slowly

Question 29

Example of system with heavy damping

Answer 29

A spring in thick oil

Question 30

How does the amplitude of an oscillation change with critical damping?

Answer 30

the time taken for displacement to become zero is a minimum

Question 31

Example of critical damping

Answer 31

Shock absorbers of a car

Question 32

What happens if oscillations are forced on ductile materials

Answer 32

Energy will be absorbed due to plastic deformation and motion will be damped

Question 33

Resonance

Answer 33

Takes place when the applied frequency equals the natural frequency of an oscillator

Question 34

In theory what should happen to amplitude of a system in resonance?

Answer 34

It should be infinite as energy is continually being put into the system but in practise it is reduced by damping

Question 35

How does damping affect the resonant frequency

Answer 35

If damping is increased the resonance occurs at a lower frequency

Question 36

How does damping affect the amplitude

Answer 36

It reduces the amplitude

Question 37

Examples of resonance occurring?

Answer 37

* opera singer smashing glass * microwaves * radios

Question 38

Which of the following can’t apply to the oscillations of a system undergoing resonance? A) damped B) driven C) forced D) free

Answer 38

D) free

Question 39

When a mass on a spring is in the equilibrium position, what is the elastic potential?

Answer 39

At a maximum

Question 40

During an earthquake, steel framed buildings absorb energy because steel is A) ductile B) elastic C) stiff D) strong

Answer 40

A) ductile

Question 41

How do spring dampers reduce the amplitude of an oscillating bridge?

Answer 41

* they absorb energy * the springs oscillate with the natural frequency * hence there is max transfer of energy * spring must not return energy back to bridge

Question 42

Which of the following is not an example of SHM? A) a car bouncing on its suspension system B) a child bouncing on a trampoline C) a person bouncing on a bungee cord D) a swinging pendulum in a grandfather clock

Answer 42

B) a child jumping on a trampoline

Question 43

When will the motion of a mass bouncing on the end of a vertical spring be simple harmonic? A) if the string can store energy B) if it has elasticity C) is hung vertically D) obeys hookes law

Answer 43

D) obeys hookes law

Question 44

Damping is used to prevent a bridge from oscillating, it will A) increase the stiffness of the bridge B) increase the natural frequency of the bridge C) dissipated energy from the bridge D) decrease the forcing frequency on the bridge

Answer 44

C) dissipate energy from the bridge

Question 45

The damping force acting on an oscillating system is always A) in the opposite direction to acceleration B) in the opposite direction to velocity C) in the same direction as acceleration D) in the same direction as velocity

Answer 45

B) in the opposite direction to velocity

Question 46

When a mass is oscillating on a vertical spring which obeys hookes law what happens to the time period over time?

Answer 46

It stays constant because the spring obeys hookes law