Unit 1 Defenitions

Question 1

Scalar

Answer 1

Quantity with size only, e.g., distance

Question 2

Vector

Answer 2

Quantity with size and direction, e.g., velocity

Question 3

Friction

Answer 3

Force opposing motion

Question 4

Newton’s First Law

Answer 4

If there is no resultant force an object it will :
-stay at rest
-or moves with uniform velocity

Question 5

Newton’s Second Law

Answer 5

A resultant force will cause an object to accelerate
The acceleration is directly proportional to the size of the resultant force and acts in the same direction

Question 6

Weight

Answer 6

Force due to gravity on an object

Question 7

Mass

Answer 7

Amount of matter in a body

Question 8

Acceleration of free fall, ‘g’

Answer 8

g = 10 m/s2.
The acceleration of an object allowed to fall freely from rest

Question 9

Retardation

Answer 9

Negative acceleration or deceleration

Question 10

Hooke’s law

Answer 10

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

Question 11

Moment of a force

Answer 11

Force applied multiplied by perpendicular distance from the pivot

Question 12

Principle of Moments

Answer 12

When an object is in equilibrium the total clockwise moment about a point equals the total anticlockwise moment about the same point

Question 13

Centre of Gravity

Answer 13

Point where object’s weight appears to act

Question 14

Density

Answer 14

Mass per unit volume of material

Question 15

Pressure

Answer 15

Force per unit cross-sectional area

Question 16

Principle of Conservation of Energy

Answer 16

Energy cannot be created or destroyed, but can be changed from one form to another
The total amount of energy does not change

Question 17

Renewable source

Answer 17

Resource which is naturally replenished within a human lifetime

Question 18

Non-renewable source

Answer 18

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

Question 19

Work done

Answer 19

Force applied multiplied by distance moved

Question 20

Kinetic energy

Answer 20

Energy possessed by a moving object

Question 21

Gravitational potential energy

Answer 21

Energy possessed due to an objects position (height) in a gravitational field

Question 22

Power

Answer 22

Rate at which work is done
Amount of work done (or energy transferred) in 1 second.

Question 23

Efficiency

Answer 23

Fraction of input energy as useful output

Question 24

Rutherford-Bohr model of atom

Answer 24

Small, dense, positive nucleus surrounded by shells of orbiting electrons

Question 25

Atomic number Z

Answer 25

Total protons in an atom's nucleus

Question 26

Mass number A

Answer 26

Total protons and neutrons in an atom's nucleus

Question 27

Isotope

Answer 27

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

Question 28

Radioactive

Answer 28

Unstable nucleus which randomly and spontaneously decays by emitting radiation (alpha, beta or gamma)

Question 29

Background radiation

Answer 29

Radiation detected when no radioactive sources are present

Question 30

Half Life

Answer 30

Time taken for the activity to fall to half its original value.

Question 31

Alpha radiation

Answer 31

Particle identical to a helium nucleus; 2 protons and 2 neutrons Charge +2 Mass 4u

Question 32

Beta radiation

Answer 32

Fast electron emitted from unstable nucleus Charge -1 Mass 1/1836 u

Question 33

Gamma radiation

Answer 33

High energy electromagnetic radiation

Question 34

Ionisation

Answer 34

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

Question 35

Fission

Answer 35

The splitting of a heavy nucleus (by absorption of a neutron) into 2 or more smaller nuclei, 2 or 3 neutrons and a large amount of energy

Question 36

Fusion

Answer 36

The joining of 2 light nuclei to form a heavier nucleus, releasing a large amount of energy.

Question 37

Conduction

Answer 37

Heat transfer through solids - When heated the atoms vibrate faster and with a bigger amplitude (larger vibrations). - They collide with neighbouring atoms and pass the heat energy along in the form of kinetic energy.

Question 38

Conductor

Answer 38

A material which allows heat to pass through it easily (Metals are good conductors because they have free electrons) - the free electrons gain kinetic energy. - They move faster and transfer the energy through the metal by colliding into multiple atoms This method is much quick than passing from atom to atom

Question 39

Convection

Answer 39

Method of heat transfer in liquids and gas This method involves the movement of particles

Question 40

Convection current

Answer 40

Particles above heat source gain kinetic energy - This causes them to move faster and further apart - This part of liquid/gas becomes less dense and rises - Cooler particles take the place of the particles which rose

Question 41

Radiation

Answer 41

Heat travelling in self-supporting electromagnetic waves