component 1

Question 1

Quantity

Answer 1

In S.I. a quantity is represented by a number x a unit,

e.g. m = 3.0 kg

Question 2

Scalar

Answer 2

A scalar is a quantity that has magnitude only.

Question 3

Vector

Answer 3

A vector is a quantity that has magnitude and direction

Question 4

The principle of moments

Answer 4

For a system to be in equilibrium, the sum of anticlockwise
moments about a point = sum of clockwise moments about
the same point.

Question 5

Centre of gravity

Answer 5

The centre of gravity is the single point within a body at
which the entire weight of the body may be considered
to act

Question 6

Newtons 1st Law

Answer 6

An object remains in the same state of motion unless a resultant force acts on it

Question 7

Newton’s 2nd law

Answer 7

The rate of change of momentum of an object is
proportional to the resultant force acting on it, and
takes place in the direction of that force, or f=ma

Question 8

Newtons 3rd law

Answer 8

If a body A exerts a force on a body B, then B exerts

an equal and opposite force on A.

Question 9

The principle of conservation of momentum

Answer 9

The vector sum of the momenta of bodies in a system
stays constant even if forces act between the bodies,
provided there is no external resultant force.

Question 10

Elastic collision

Answer 10

A collision in which there is no change in total kinetic

energy

Question 11

Inelastic collision

Answer 11

A collision in which kinetic energy is lost.

Question 12

Work, W

Answer 12

Work done by a force is the product of the magnitude
of the force and the distance moved in the direction of
the force.

Question 13

Principle of conservation of energy

Answer 13

Energy cannot be created or destroyed, only
transferred from one form to another. Energy is a
scalar.

Question 14

Simple harmonic motion (shm)

Answer 14

Shm occurs when an object moves such that its
acceleration is always directed toward a fixed point
and is proportional to its distance from the fixed point.

The motion of a point whose displacement x changes
with time t according to x = A sin (ω t + ε), where A, ω
and ε are constants.

Question 15

Amplitude, A of an oscillating object

Answer 15

The maximum value of the object’s displacement (from

its equilibrium position).

Question 16

Phase of an oscillation

Answer 16

The phase of an oscillation is the angle (ωt + ε) in the
equation x = A sin (ω t + ε). [ε is called the phase
constant.]

Question 17

Free oscillations

[Natural oscillations]

Answer 17

Free oscillations occur when an oscillatory system
(such as a mass on a spring, or a pendulum) is
displaced and released.
[The frequency of the free oscillations is called the
system’s natural frequency.]

Question 18

Damping

Answer 18

Damping is the dying away, due to resistive forces, of

the amplitude of free oscillations

Question 19

Critical damping

Answer 19

Critical damping is the case when the resistive forces
on the system are just large enough to prevent
oscillations occurring at all when the system is
displaced and released.

Question 20

Forced oscillations

Answer 20

These occur when a sinusoidally varying ‘driving’ force
is applied to an oscillatory system, causing it to
oscillate with the frequency of the applied force

Question 21

Resonance

Answer 21

If, in forced vibrations, the frequency of the applied
force is equal to the natural frequency of the system
(e.g. mass on spring), the amplitude of the resulting
oscillations is large. This is resonance

Question 22

Ideal gas

Answer 22

An ideal gas strictly obeys the equation of state
pV = nRT, in which n is the number of moles, T is the
kelvin temperature and R is the molar gas constant.
R = 8.31 J mol-1 K-1

. With the exception of very high
densities a real gas approximates well to an ideal gas.

Question 23

The mole

Answer 23

The mole is the S.I. unit of an ‘amount of substance’. It
is the amount containing as many particles (e.g.
molecules) as there are atoms in 12 g of carbon-12.

Question 24

Avogadro constant, NA

Answer 24

This is the number of particles per mole.

Question 25

Internal energy, U, of

a system

Answer 25

This is the sum of the kinetic and potential energies of

the particles of a system

Question 26

Heat, Q

Answer 26

This is energy flow from a region at higher temperature
to a region at lower temperature, due to the
temperature difference. In thermodynamics we deal
with heat going into or out of a system. It makes no
sense to speak of heat in a system

Question 27

Work, W

Answer 27

If the system is a gas, in a cylinder fitted with a piston,
the gas does work of amount p x (change in) V when it exerts a pressure p and pushes the piston out a small way, so the gas volume increases by (change in) V. Work, like heat, is energy in transit from (or to) the system

Question 28

First law of thermodynamics

Answer 28

The increase, (change in) U, in internal energy of a system is (change in) U = Q – W in which Q is the heat entering the system and W is the work done by the system. Any of the terms in the equation can be positive or negative, e.g. if 100 J of heat is lost from a system Q = –100 J.

Question 29

Define temperature

Answer 29

A measure of the average kinetic energy of particles in a system