Unit 4

Question 1

What is the principle of linear momentum?

Answer 1

Total momentum of two objects before they collide is equal to the total momentum after they collide assuming no external forces act.

Question 2

Define elastic collision

Answer 2

A collision where kinetic energy is conserved

Question 3

Inelastic collision

Answer 3

Collision where kinetic energy isn’t conserved

Question 4

In a Inelastic collision what other forms could the energy be converted into?

Answer 4

Heat energy, sound energy, or energy into damaging the vehicles

Question 5

What is newtons 2nd law

Answer 5

Force is proportional to the rate of change of momentum

Question 6

What is impulse

Answer 6

Impulse is force x time and equal to the change in momentum

Question 7

What is represented by the area under a force time graph?

Answer 7

Impulse or change in momentum

Question 8

Why are objects moving in a circle constantly accelerating even though they are travelling at constant speed?

Answer 8

The centripetal force acts perpendicular to the objects velocity causing it to move in a circle and velocity is constantly changing even though speed I constant because the direction it is moving in is always changing

Question 9

Where is the acceleration towards when an object is moving in a circle?

Answer 9

Toward the centre of the circle

Question 10

Define simple harmonic motion

Answer 10

Oscillations in which the acceleration is directly proportional to the displacement and acting in the opposite direction (towards equilibrium)

Question 11

Defining equation of SHM

Answer 11

A=(2pif)^2 x

Question 12

What is the phase difference between the velocity and displacement of an object undergoing SHM.

Answer 12

Pi over 2 (1/4 of a wave cycle)

Question 13

What is the phase difference between the acceleration and displacement of an object undergoing SHM?

Answer 13

Pi radians - they are completely out of phase

Question 14

What is the relationship between the amplitude and time period of a simple pendulum?

Answer 14

They are independent of each other - the time period is the same no matter what the amplitude of oscillation is

Question 15

What are the two types of potential energy in a spring- mass system

Answer 15

Gravitational and elastic potential

Question 16

When is the kinetic energy + potential energy = constant?

Answer 16

In an undamped system

Question 17

How can you derive the equation of the time period of a mass spring system?

Answer 17

Using f=ma where F=kx (hookes law) and simple harmonic equTion for acceleration

Question 18

How do you work out the spring constants of springs in parallel? (Side by side)

Answer 18

K(total)=k1 +k2 +…

Question 19

How do you work out the springs constant of springs in series?

Answer 19

The inverse of the spring constants are added together

Question 20

What is a free oscillation

Answer 20

Oscillation with no transfer of energy to and from the surroundings- there is no driving force acting and the object oscillates at its natural frequency

Question 21

What causes forced vibrations?

Answer 21

A periodic external force

Question 22

When does resonance occur?

Answer 22

When the driving frequency equals the natural frequency

Question 23

At driving frequencies lower than the natural frequency what is the phase difference?

Answer 23

No phase difference they are in phase

Question 24

What is the phase difference between the driver and oscillator at resonance?

Answer 24

Phase difference between the oscillator and driver is 90 degrees (Pi over 2)

Question 25

Phase difference between driver and oscillator at frequencies higher than the natural frequency

Answer 25

Driver completely out of phase

Question 26

What does damping do to SHM oscillations

Answer 26

Decrease the amplitude

Question 27

Define light damping

Answer 27

The amplitude of oscillation reduces a small amount with each period and can take a long time to stop oscillating

Question 28

Define heavy damping

Answer 28

Amplitude gets much smaller in a short space of time and stop oscillating quicker than a lightly damped system

Question 29

Define Critical damping

Answer 29

Reduces amplitude and stops the system oscillating in the shortest time possible

Question 30

Where can critical damping be used?

Answer 30

In car suspension systems

Question 31

Deign overdamping

Answer 31

Take longer to reach equilibrium than critically damped systems

Question 32

Example where overdamping is used and explain why

Answer 32

Heavy doors- they are over damped so they don't slam shut too quickly, they close slowly to give People time to walk through them

Question 33

Explain the difference in resonance graphs for damped systems and what happens to when resonance occurs for heavily damped systems

Answer 33

Lightly damped systems have a very sharp resonance peak where as heavily damped systems have a latter response. For heavy damping resonance occurs at a slightly lower driving frequency than the natural frequency.

Question 34

Examples of uses of damping

Answer 34

Bridges/buildings - damped to avoid them being damaged by resonance in regions prone to earthquakes. Heavy masses move in opposite direction to building to dampen the oscillations - critical damping. Other uses are loud speakers

Question 35

Define gravitational,field strength

Answer 35

Force per unit mass

Question 36

Define gravitational potential

Answer 36

Work done per unit mass in moving the object from infinity to that point in the gravitational field

Question 37

What is the gradient of a gravitational potential against distance graph?

Answer 37

Field strength

Question 38

What is the area under a field strength-distance graph

Answer 38

Gravitational potential

Question 39

What is the gravitation potential at a infinite distance from the mass

Answer 39

0

Question 40

Gravitational potential is always...

Answer 40

Negative

Question 41

Momentum- vector or scalar

Answer 41

Vector