APH4001 Particles, Waves & Quanta

Question 1

Define Velocity

Answer 1

The rate of change of position with time

Question 2

Define Acceleration

Answer 2

The rate of change of velocity with time

Question 3

What is Newton’s First Law?

Answer 3

An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force

Question 4

What is Newton’s Second Law?

Answer 4

The rate of change of momentum is directly proportional to the net force applied, in the direction of the applied force

Question 5

What is Newton’s Third Law?

Answer 5

When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude & opposite in direction of the first body

Question 6

Define Momentum

Answer 6

In the absence of external forces, a body at rest will stay at rest and in motion will continue with the same inertia

Question 7

Define the Work-Energy Theorem

Answer 7

The net work done on an object equals its Kinetic Energy, K

Question 8

Define Potential Energy

Answer 8

The negative integral of the force, and it follows that the force is the negative derivative of the potential energy

Question 9

Define Gravitational Potential Energy

Answer 9

The energy an object possesses because of its position in a gravitational field

Question 10

Define Power

Answer 10

The rate at which work is performed with respect to time

Question 11

Define Radian

Answer 11

1 radian is the angle at which the arc has the same length as the radius. Radian=arc/radius

Question 12

Define Angular Velocity

Answer 12

The rate of change of the angle with respect to time

Question 13

Define Angular Acceleration

Answer 13

The time derivative of the angular velocity vector
OR
The rate of change of angular velocity with respect to time

Question 14

Define Moment of Inertia

Answer 14

The product of the mass of a particle & the square of its distance from the centre of rotation

the torque required to achieve a particular angular acceleration along a rotational axis

Question 15

Define Torque

Answer 15

The measure of the tendency of a force to cause or change a bodies rotational motion
Rate at which angular momentum changes

T = rFsin

Question 16

Define Angular Momentum

Answer 16

The rotational analogue of linear momentum

Question 17

Define Coulombs Law

Answer 17

Charges interact with a force proportional to the product of the charges and inversely proportional to the distance between them

Question 18

What is the Principle of Superposition?

Answer 18

If one charge is involved, the net force is the vector sum of all forces

Question 19

Define Magnetic Domain

Answer 19

A region in which the magnetic fields of atoms are grouped together and aligned

Question 20

What is Einstein’s 1st Postulate?

Answer 20

The laws of Physics are the same in every inertial frame of reference

Question 21

What is Einstein’s 2nd Postulate?

Answer 21

The speed of light in a vacuum is the same in all inertial frames of reference and is independent of the motion of the source

Question 22

Define the Ultimate Speed Limit

Answer 22

It is impossible for an inertial observer to travel at the speed of light,c

Question 23

Define Inertial Frame

Answer 23

A reference frame with constant linear velocity

Question 24

Define Non-Inertial Frame

Answer 24

A reference frame without constant linear velocity

Question 25

Define Time Dilation

Answer 25

The difference in the elapsed time measured by two observers

Question 26

Define Amplitude

Answer 26

The maximum magnitude of displacement from equilibrium

Question 27

Define Frequency

Answer 27

The number of cycles in a unit of time

Question 28

Define Angular Frequency

Answer 28

The rate of change of angular quantity

Question 29

Define Time period

Answer 29

The time taken for one complete cycle of a wave

Question 30

Define Simple Harmonic Motion (SHM)

Answer 30

An oscillation where the restoring force is directly proportional to the displacement from the equilibrium

Question 31

Define Harmonic Oscillator

Answer 31

A body that undergoes SHM

Question 32

Define Mechanical Wave

Answer 32

A disturbance that travels through a medium. The particles in the medium undergo displacement

Question 33

Define Transverse Wave

Answer 33

Particles undergoing perpendicular displacement to the direction of the wave

Question 34

Define Longitudinal Wave

Answer 34

Particles undergo displacement in line with the motion of the wave

Question 35

Define Wave Function

Answer 35

The vertical displacement of the wave, y, is a function of both the horizontal displacement, x, and time, t. y=y(x,t)

Question 36

Define Phase Velocity

Answer 36

The rate at which the phase of a wave propagates in space

Question 37

Define Damping

Answer 37

The decrease in amplitude caused by a dissipative force

Question 38

Define Forced Oscillation

Answer 38

When a Sinusoidally varying force is added to a damped harmonic oscillator

Question 39

Define Beating

Answer 39

The periodic variation in the amplitude at a given point due to superposition of two waves having slightly different frequencies

Question 40

Define the Photoelectric Effect

Answer 40

When a photon collides with an electron, that electron is knocked out of obit of the atom, the photon ceases to exist. This only takes place if the photon has a high enough energy

Question 41

Define Excited State

Answer 41

A photon can collide with an electron to bring it to a higher state in that electron

Question 42

Define the Compton Effect

Answer 42

A photon can scatter from an electron & in the process it looses some of its energy. In such a case the photon has a lower frequency but still travels at the speed of light

Question 43

Define Pair Production

Answer 43

A photon creates an electron & positron. In this process the photon will disappear

Question 44

Define the Photoelectric Effect

Answer 44

Emission, or rejection, of electrons from the surface of, generally, a metal in response to an incident light

Question 45

What are the transformations to turn Cartesian co-ordinates into Spherical co-ordinate?

Answer 45

r=√(x^2+y^2+z^2 ) θ=tan^(-1)((√(x^2+y^2 )/z) ϕ=cos^(-1)( z/r)

Question 46

What are the transformations to turn Spherical co-ordinates into Cartesian co-ordinates?

Answer 46

x=r cosθ sinϕ y=r sinθ cosϕ z=r cosϕ

Question 47

What is the general equation for a scalar product?

Answer 47

a. b= |a| x |b| x cosθ | a. b= ax x bx + ay x by + az x bz

Question 48

What is the general equation for a cross product

Answer 48

axb= |a| x |b| x sinθ

Question 49

What are the suvat equations?

Answer 49

``` v=u + at s=ut + 1/2at^2 s=vt - 1/2at^2 v^2=u^2 + 2as s= (u + v)/2 x t ```

Question 50

What is the equation for impulse?

Answer 50

F= dp/dt

Question 51

What is the work done equation

Answer 51

W=Fs.cosθ

Question 52

What does the law of conservation state?

Answer 52

That the all forms of energy are conserved in the system in an ideal world i.e. energy before = energy after

Question 53

Define Power and state its equation

Answer 53

The rate of change of work done with respect to time | dW/dt