Module 1 definitions

Question 1

Define a vector quantity

Answer 1

Has both magnitude and direction

Question 2

Define a scalar quantity

Answer 2

Only contains magnitude and no direction

Question 3

Define velocity

Answer 3

The rate of change of displacement

Question 4

Define displacement

Answer 4

The distance travelled in a particular direction

Question 5

Define instantaneous speed

Answer 5

The speed of an object at a given point in time.

Question 6

Define acceleration

Answer 6

The rate of change of velocity of an object

Question 7

Define stopping distance

Answer 7

The total distance travelled from when the driver first sees a reason to stop, to when the vehicle stops.

Question 8

Define thinking distance

Answer 8

The distance travelled by the vehicle from when the driver sees a problem and then brakes are applied.

Question 9

Braking distance

Answer 9

The distance travelled by a vehicle after applying the brakes.

Question 10

Define mass

Answer 10

The amount of matter

Question 11

Weight

Answer 11

The gravitational force on an object

Question 12

Centre of mass

Answer 12

An imaginary point where the entire weight of an object appears to act.

Question 13

Centre of gravity

Answer 13

A point where the weight appears to act.

Question 14

Drag

Answer 14

A frictional force that opposes the motion of the object

Question 15

Terminal velocity

Answer 15

The constant speed reached by an object when the drag force is equal and opposite the weight of the object

Question 16

Moment

Answer 16

The product of force and the perpendicular distance from a pivot.

Question 17

Principle of moment

Answer 17

For a body in rotational equilibrium, the sum of anticlockwise moments about any pivot is equal to the sum of the clockwise moments about the same point.

Question 18

Torque

Answer 18

The product of one of the forces and the perpendicular separation between the forces

Question 19

Density

Answer 19

Mass per unit volume

Question 20

Fluid

Answer 20

Any substance that can flow

Question 21

Archimedes principle

Answer 21

The upthrust exerted in a body immersed in a fluid, whether full or partially submerged is equal to the weight of the fluid that the body displaces.

Question 22

Work done

Answer 22

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

Question 23

Kinetic energy

Answer 23

Energy associated to the movement of an object

Question 24

Gravitational potential energy

Answer 24

The energy due to the position of an object in the Earth’s gravitational field.

Question 25

Principle of conservation of energy

Answer 25

Energy cannot be created or destroyed only transferred from one form to another.

Question 26

Power

Answer 26

Rate of work done

Question 27

Extension

Answer 27

The increase in length of an object when a tensile force is exerted on it

Question 28

Tensile force

Answer 28

Equal and opposite forces acting on a material to stretch it

Question 29

Tensile deformation

Answer 29

A change in shape of a object due to tensile forces

Question 30

Compressive deformation

Answer 30

A change in the shape of an object dude to the compressive forces

Question 31

Hooke’s law

Answer 31

The force applied is directly proportional to the extension of the spring unless the limit of proportionality is exceeded.

Question 32

Plastic deformation

Answer 32

An irreversible change in the shape of an object due to a tensile force. The removal of the force produces a permanent deformation.

Question 33

Elastic deformation

Answer 33

A reversible change in the shape of an object due to a tensile force. The removal of the force will return the object back to its original shape and size.

Question 34

Elastic potential energy

Answer 34

The energy stored in a object due to its deformation

Question 35

Tensile stress

Answer 35

The force per unit cross sectional area.

Question 36

Tensile Strain

Answer 36

The extension per unit length

Question 37

Limit of proportionality

Answer 37

The value of force beyond which stress is no longer proportional to strain.

Question 38

Ultimate tensile strength

Answer 38

The maximum stress that material can withstand before it breakss

Question 39

Young modulus

Answer 39

The ratio of tensile stress to tensile strain when the quantities are directly proportional to each other.

Question 40

Newtons first law

Answer 40

A body will remain at rest or continue to move with constant velocity unless acted upon by a resultant force

Question 41

Newtons second law

Answer 41

The rate of change of momentum of an object is directly proportional to the resultant force and it takes place is the direction of the force.

Question 42

Newtons third law

Answer 42

When two object interact, each exert equal but opposite forces on the other during the interaction.

Question 43

Momentum

Answer 43

The product of mass and the velocity of the mass

Question 44

Conservation of momentum

Answer 44

For a system of interacting objects the total momentum in an specific direction remains constant as long as no external forces act on the system

Question 45

Inelastic collision

Answer 45

A collision in which kinetic energy is transferred in other forms eg heat

Question 46

Elastic collisions

Answer 46

Momentum and kinetic energy are conserved

Question 47

Impulse

Answer 47

The product of a force and the time for which the force acts

Question 48

Couple

Answer 48

A pair of parallel forces pointing in the opposite direction

Question 49

Newton

Answer 49

When 1kg of mass has an acceleration of 1ms-2.

Question 50

Free fall

Answer 50

The motion of an object accelerating under gravity with no other force acting on it.

Question 51

Efficiency

Answer 51

The ratio of useful output energy to total input energy.

Question 52

Elastic limit

Answer 52

The value for stress or force beyond which elastic deformation becomes plastic deformation and the material will no longer return to its original shape and size when the stress or force is removed.

Question 53

Yield points

Question 54

Tension

Answer 54

The pulling force exerted by a string, cable or chain on an object.

Question 55

Normal contact force

Answer 55

The force exerted by a surface on an object, which acts perpendicularly to the surface.

Question 56

Upthrust

Answer 56

The upward buoyant force exerted on a body immersed in a fluid.

Question 57

Friction