Definitions

Question 1

Define scaler

Answer 1

Quantity which has size only e.g. distance, speed

Question 2

Define vector

Answer 2

Quantity which has both size and direction e.g. displacement, velocity

Question 3

Define displacement

Answer 3

Distance travelled from start; area under velocity-time graph.

Question 4

Define velocity

Answer 4

Rate of change of displacement; gradient of a displacement-time graph

Question 5

Define acceleration

Answer 5

The rate of change of velocity; gradient of a velocity-time graph

Question 6

Define friction

Answer 6

A force which opposes motion

Question 7

Define newton’s first law

Answer 7

An object will continue to move in a straight line at a constant speed unless an unbalanced force acts on it.

Question 8

Define newton’s second law

Answer 8

A resultant force will cause an object to accelerate and the acceleration is proportional to the size of the resultant force

Question 9

Define newton’s third law

Answer 9

To every action force there is an equal and opposite reaction force

Question 10

Define weight

Answer 10

The force due to the pull of gravity on an object

Question 11

Define mass

Answer 11

The amount of matter in a body

Question 12

Define acceleration of free fall, ‘g’

Answer 12

10 m/s², the acceleration of an object allowed to fall freely from rest

Question 13

Define hooke’s law

Answer 13

The extension of a spring is directly proportional to the applied force, provided that the limit of proportionality is not exceeded

Question 14

Define spring constant

Answer 14

A measure of the stiffness of a spring; gradient of a force-extension graph

Question 15

Define principle of moments

Answer 15

In equilibrium the total clockwise moment about a point equals the total anticlockwise moment about the same point

Question 16

Define centre of gravity

Answer 16

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

Question 17

Define principle of conservation of energy

Answer 17

Energy can be changed from one form to another form but the total amount of energy does not change

Question 18

Define renewable source

Answer 18

Resource which is naturally replenished within a human lifetime

Question 19

Define non-renewable source

Answer 19

Resource with a finite supply of energy which will run out some time

Question 20

Define atomic number Z

Answer 20

The total number of protons in the nucleus of an atom

Question 21

Define mass number A

Answer 21

The total number of protons plus neutrons in the nucleus of an atom

Question 22

Define isotope

Answer 22

Different forms of the same element with the same atomic number (and no. of protons) but different mass numbers (and no. of neutrons)

Question 23

Define radioactive

Answer 23

Unstable nucleus which spontaneously emits radiation

Question 24

Define background radiation

Answer 24

Radiation detected when no radioactive sources are present

Question 25

Define ionisation

Answer 25

Changing a neutral atom into a charged ion by removing an electron.

Question 26

Define half life

Answer 26

The time it takes for half the radioactive nuclei to decay. (Or for the activity to fall to half its original value.)

Question 27

Define alpha radiation

Answer 27

Same as a helium nucleus; 2 protons and 2 neutrons

Question 28

Define beta radiation

Answer 28

Fast moving electron from the nucleus

Question 29

Define gamma radiation

Answer 29

High energy electromagnetic radiation

Question 30

Define fission

Answer 30

The splitting of a heavy nucleus (by absorption of a neutron) into 2 or more smaller nuclei, a few neutrons and a large amount of energy.

Question 31

Define fusion

Answer 31

The joining of 2 light nuclei to form a heavier nucleus, releasing a large amount of energy (very high temperature needed)