Mechanics

Question 1

Scalar Quantity

Answer 1

Quantity which has magnitude - distance, time, speed and energy

Question 2

Vector Quantity

Answer 2

Quantity which has magnitude and direction - displacement, velocity, force and momentum

Question 3

Displacement

Answer 3

The distance is a given direction

Question 4

Velocity

Answer 4

The rate of change of displacement

Question 5

Acceleration

Answer 5

The rate of change of velocity

Question 6

Force

Answer 6

The rate of change of momentum

Question 7

Impulse

Answer 7

Change in momentum

Question 8

Resultant Force

Answer 8

Single force which has the combined effect of two or more forces

Question 9

Equilibrium

Answer 9

Resultant force acting on an object is equal to zero
- Forces form a closed triangle
- Object is either stationary or moves at constant velocity

Question 10

Moment

Answer 10

Turning effect of a force
- Moment = Force x perpendicular distance from the line of action of the force to the pivot

Question 11

Principle of Moments

Answer 11

For an object in equilibrium - sum of all anticlockwise moments about any point must equal the sum of all the clockwise moments about that point

Question 12

Couple

Answer 12

Pair of equal but opposite coplanar forces

Question 13

Torque

Answer 13

Turning effect of a couple

Question 14

Centre of mass

Answer 14

Point where all the mass of an object can be thought to be concentrated
- Use of lines of symmetry to find centre of mass of an object

Question 15

Displacement time-graph

Answer 15

Displacement (y-axis) against time (x-axis)
Gradient = equal instantaneous velocity

Question 16

Velocity-time graph

Answer 16

Velocity (y-axis) against time (x-axis)
- Area underneath = displacement
- Gradient = acceleration

Question 17

Acceleration-time graph

Answer 17

Acceleration (y-axis) against time (x-axis)
- Area = change in velocity

Question 18

Average velocity

Answer 18

Velocity of an object over a given time period
- Average velocity = total displacement/ total time

Question 19

Newton’s First Law

Answer 19

Object remains at rest or remains in uniform motion unless acted upon by a force

Question 20

Newton’s Second Law

Answer 20

Acceleration of an object is directly proportional to the resultant force

Question 21

Newton’s Third Law

Answer 21

For every action, there is an equal but opposite reaction

Question 22

Conservation of Momentum

Answer 22

Interacting particle ==> Total momentum is constant provided no external force acts upon the system

Question 23

Inelastic Collision

Answer 23

A collision where kinetic energy is lost

Question 23

Elastic Collision

Answer 23

A collision where there is no loss of kinetic energy

Question 24

Air Resistance

Answer 24

Frictional force acting on an object moving through air, in the opposite direction to the motion of the object
- Air resistance increases with speed

Question 25

Terminal Speed

Answer 25

Maximum Velocity of a falling object
- No resultant force as the force of air resistance is equal to the weight of the object

Question 26

Acceleration due to gravity (g)

Answer 26

9.81m/s

Question 27

Impact Time

Answer 27

The duration for which the impact force acts

Question 28

Car Safety Features

Answer 28

Crumple zone, airbag and seatbelt

Safety features increase impact time, decreases the deceleration of the vehicle to decrease the impact force experienced by the occupants

Airbag also increases contact area to spread force over a greater area reduces the pressure on the body

Question 29

Power

Answer 29

Rate of energy transfer

Question 30

Efficiency

Answer 30

Proportion of total energy input transferred to useful energy output