Definitions Paper 1

Question 1

Define the term centre of mass

Answer 1

The point through which all the weight of an object is deemed to act

Question 2

Define a moment

Answer 2

A force multiplied by the perpendicular distance from the line of action of the force about the pivot

Question 3

State the principle of moments

Answer 3

For a system to be in equilibrium the total clockwise moment must equal the total anticlockwise moments about the same point

Question 4

What is the criteria for a system in equilibrium

Answer 4

The resultant force must be 0 and the resultant moment must be 0

Question 5

Define a couple

Answer 5

A pair of equal forces acting on a body but not along the same line

Question 6

Define terminal velocity

Answer 6

The maximum velocity attainable by an object as it falls through a fluid

Question 7

Define the term work done

Answer 7

The force causing a motion multiplied by the distance travelled in the direction of the motion

Question 8

State hookes law

Answer 8

The extension produced by a force in a wire or spring is directly proportional to the force applied up to the limit of proportionality

Question 9

Define specific charge

Answer 9

The ratio of the charge of a particle to its mass

Question 10

Define the term electron volt

Answer 10

One eV is the kinetic energy gained by an electron when accelerated by a potential difference of one volt

Question 11

Define the term pair production

Answer 11

A process in which a photon of EM radiation ceases to exist, creating a particle and antiparticle in its place

Question 12

Define the term annihilation

Answer 12

A process in which a particle and antiparticle collide and their masses are converted to energy in the form of a pair of photons of EM radiation

Question 13

What are strange particles

Answer 13

Particles that are produced through the strong interaction but decay through the weak interaction

Question 14

Define the term threshold frequency

Answer 14

The minimum frequency of light which causes electrons to be emitted from the surface of a metal

Question 15

Define the term work function

Answer 15

the minimum energy needed to remove an electron from the surface of a metal

Question 16

Define the term stopping potential

Answer 16

The minimum PD between two metal plates that prevents photoelectrons with the highest KE from reaching the other plate

Question 17

Define the term excitation

Answer 17

A process where an electron moves to a higher energy level

Question 18

Define the term ionisation

Answer 18

A process where an electron gains enough energy to leave the atom

Question 19

Define electric current

Answer 19

the rate of flow of charge

Question 20

Define PD

Answer 20

The work done when one coulomb of charge is moved between two points in a circuit

Question 21

Define electrical resistance

Answer 21

The ratio of the voltage across a component to the current flowing through it

Question 22

Define the term resistivity

Answer 22

A measure of how easily a material conducts electricity

Question 23

State Ohms Law

Answer 23

The current flowing through a metallic conductor is directly proportional to the PD applied across it at a constant temperature

Question 24

What is a superconductor

Answer 24

A material that has zero resistivity below a certain temperature. This critical temperature depends on the material

Question 25

Define the term electromotive force (emf)

Answer 25

The amount of energy transferred by a cell per unit charge that passes through it

Question 26

Define the term terminal potential difference

Answer 26

The voltage measured across the terminals of a cell

Question 27

What is centripetal acceleration

Answer 27

Acceleration which is always perpendicular to the velocity and always acts towards the centre of the circular motion

Question 28

What is centripetal force

Answer 28

A resultant force that always acts towards the centre of the circular motion

Question 29

What is damping

Answer 29

An effect where the energy of an oscillations object is transferred to the surroundings decreasing the amplitude of the oscillations

Question 30

Define angular speed

Answer 30

The angle through which an object moves per unit time

Question 31

What are the conditions for simple harmonic motion

Answer 31

An objects acceleration is directly proportional to displacement and is in the opposite direction

Question 32

What are free vibrations

Answer 32

Oscillations where the total energy remains constant. No external force acts on the system and it vibrates at its natural frequency

Question 33

What is resonance

Answer 33

A case where the driver frequency is equal to the natural frequency of a system causing the amplitude of oscillations to increase drastically due to an additional gain of energy from the driver