AS1

Question 1

Base units

Answer 1

Base units are the units from which all other units are derived from.

Question 2

A mole

Answer 2

defined as the number of atoms in exactly 12 grams of 12C (carbon twelve). The number is called Avogadro’s Number.

Question 3

Derived units

Answer 3

units which are defined in terms of two or more base units

Question 4

A vector

Answer 4

a physical quantity that has magnitude, direction and a unit.

Question 5

A scalar

Answer 5

a physical quantity that only has magnitude and a unit.

Question 6

The moment of a force about a point

Answer 6

the product of the force and the perpendicular distance from the point to the line- of- action of the force

Question 7

The centre of gravity of an object

Answer 7

is the point at which we can take its weight to act
through.

Question 8

The centre of mass of an object

Answer 8

is the point at which we can take its mass to be concentrated at.

Question 9

Principle of moments

Answer 9

When an object is in rotational equilibrium the sum of the clockwise moments
about any point is equal to the sum of the anticlockwise moments about the same
point.

Question 10

Displacement

Answer 10

the distance moved in a particular direction.

Question 11

Speed

Answer 11

the rate of change of distance

Question 12

Velocity

Answer 12

the rate of change of displacement.

Question 13

Acceleration

Answer 13

the rate of change of velocity.

Question 14

Projectile motion

Answer 14

when an object undergoes constant velocity in one plane and constant acceleration in the perpendicular plane or

Question 15

Newton’s first law

Answer 15

If a body is at rest, it will remain at rest unless a resultant force acts on the object.
If the body is moving in a straight line with a constant speed, it will continue to move in this way unless a resultant force acts on it.

Question 16

Newton’s second law

Answer 16

The acceleration of an object is inversely proportional to its mass,
directly proportional to the resultant force and takes place in the same direction as
the resultant force.

Question 17

Newton’s third law

Answer 17

if a body A exerts a force on body B, then body B exerts an equal and
opposite force on object A.

Question 18

Momentum of a body

Answer 18

the product of its mass and its velocity

Question 19

Principle of Conservation of Momentum

Answer 19

If no external forces are acting, the total Momentum of a system of colliding bodies is constant.

Question 20

Elastic collisions

Answer 20

those in which kinetic energy is conserved.

Question 21

Inelastic collisions

Answer 21

those in which kinetic energy is nor conserved.

Question 22

Impulse

Answer 22

the product of force and the time for which it acts.

Question 23

Energy

Answer 23

the ability to do work.

Question 24

Work

Answer 24

the product of the force and the distance moved in the direction
of the force

Question 25

Gravitational potential energy

Answer 25

the energy an object gains when it is raised above the ground.

Question 26

Kinetic energy

Answer 26

the energy possessed by a moving object

Question 27

The principle of conservation of energy

Answer 27

energy cannot be created or destroyed but can be changed from one form to another

Question 28

Power

Answer 28

the rate of doing work

Question 29

Efficiency

Answer 29

Useful power output/Total power input or Useful energy output/total energy input

Question 30

Current

Answer 30

the rate of flow of charge

Question 31

e.m.f of a battery

Answer 31

the energy converted into electrical energy when unit charge (1C) passes through it.

Question 32

The potential difference between two points

Answer 32

the energy generated for every coulomb of charge passing between them.

Question 33

Electrical power

Answer 33

the rate at which electrical energy is converted into other forms of energy by a circuit or a component.

Question 34

Ohm’s law

Answer 34

states that the current through a metallic conductor is directly proportional to the applied p.d. provided the temperature is constant

Question 35

Resistance

Answer 35

the opposition to the flow of current through a conductor -the ratio of the potential difference across a conductor to the current flowing through it i.e R = V/I

Question 36

Resistivity

Answer 36

numerically equal to the resistance of a sample of the material 1m long and of cross section 1m^2

Question 37

Internal resistance

Answer 37

the opposition to the flow of current through the cell/power supply.

Question 38

Superconductivity

Answer 38

We can define a material as a superconductor if it loses all its electrical resistivity to become a perfect conductor when it is below its critical temperature