Module 3 Definitions and Statements

Question 1

Define simple harmonic motion.

Answer 1

Force/acceleration is proportional to displacement (from equilibrium position)
(Resultant force) force/acceleration is (always) towards equilibrium position

Question 2

State the principle of moments

Answer 2

(When an object is in equilibrium the) sum of clockwise moments (about a point) = sum of anticlockwise moments (about the same point)

Question 3

Define velocity.

Answer 3

velocity = rate of change of displacement

Question 4

Define acceleration.

Answer 4

acceleration = rate of change of velocity

Question 5

Define thinking distance.

Answer 5

The distance travelled (by the car) from when the driver sees a problem and the brakes are applied

Question 6

Define work done by a force.

Answer 6

work done = force x distance moved in direction of force

Question 7

Explain the term drift velocity

Answer 7

Drift velocity: average mean/net/overall velocity of electron along wire

Question 8

Define the newton.

Answer 8

Force is 1 N when a 1 kg mass has an acceleration of 1 m s–2

Question 9

Define a couple

Answer 9

Two equal but opposite forces

Question 10

Define the torque of a couple

Answer 10

torque = one of the forces x perpendicular distance between the forces

Question 11

Define density

Answer 11

density = mass/volume or ‘density is mass per

(unit) volume’

Question 12

Define braking distance of a car.

Answer 12

The distance travelled (by the car) whilst the brakes are applied and the car stops

Question 13

State two conditions necessary for an object to be in equilibrium

Answer 13

Net / total / resultant force = 0

Net / total torque / moment = 0

Question 14

Define moment of a force

Answer 14

moment = force x perpendicular distance from point / pivot

Question 15

Define centre of gravity

Answer 15

The point where the weight (appears) to act

Question 16

State the principle of conservation of energy.

Answer 16

Energy cannot be created or destroyed; it can only be transferred/transformed into other forms
or
The (total) energy of a system remains constant
or
(total) initial energy = (total) final energy (AW)

Question 17

Define the Young modulus of a material.

Answer 17

Young modulus = stress/strain

As long as elastic limit is not exceeded

Question 18

Define the watt.

Answer 18

1 J (of work done) per second

Question 19

Define power

Answer 19

power = work done/ time
or energy/time
or ‘rate of work done’

Question 20

State Hooke’s law

Answer 20

Extension is proportional to force (applied as long as the elastic limit is not exceeded)

Question 21

Explain what is meant by plastic deformation.

Answer 21

Material is permanently deformed / longer when stress / force is removed

Question 22

Define ultimate tensile strength of a material.

Answer 22

Maximum stress material can withstand (before

fracture)

Question 23

Define the force constant of a spring.

Answer 23

force/extension or force per (unit) extension

Question 24

State Hooke’s law for a material in the form of a wire and state the conditions under
which this law applies.

Answer 24

the force (needed to stretch a spring is directly) is proportional to the extension (of the spring from its natural length) up to the limit of proportionally

Question 25

Explain what is meant by the elastic limit of the wire

Answer 25

the maximum amount that a material can be stretched (by a force) and still return to its original length when the force is removed

Question 26

State the meaning of

tensile stress

Answer 26

stretching) force (applied) per unit cross-sectional area

Question 27

State the meaning of tensile strain

Answer 27

extension (produced) per unit length

Question 28

State in words Newton’s second law of motion

Answer 28

(Resultant) force (acting on an object) is (directly) proportional to the rate of change of momentum (and occurs in the same direction)

Question 29

Define the impulse of a force

Answer 29

Force x time for which the force acts / duration of collision

Question 30

Define linear momentum.

Answer 30

(linear momentum =) mass x velocity

Question 31

State the principle of conservation of linear momentum

Answer 31

Total momentum is constant/conserved for a closed system/provided no external forces

Question 32

Explain what is meant by an inelastic collision.

Answer 32

Some loss of kinetic energy during collision

Question 33

State Newton’s second and third laws of motion.

Answer 33

Force is proportional to the rate of change of momentum
When one body exerts a force on another the other body exerts an equal (in magnitude) and opposite (in direction) force on the first body