Definitons Mechanics

Question 1

displacement

Answer 1

the distance moved by an object in a particular direction.

Question 2

instantaneous speed

Answer 2

the speed at the precise instant that it is measured (e.g. a car’s speedometer).

Question 3

average speed

Answer 3

the speed calculated during a period of time.

Question 4

speed

Answer 4

rate of change of distance

Question 5

velocity

Answer 5

rate of change of displacement

Question 6

acceleration

Answer 6

rate of change of velocity

Question 7

density

Answer 7

mass/volume

Question 8

torque of a couple

Answer 8

one of the forces x perpendicular distance between the forces

Question 9

moment of a force

Answer 9

force x perpendicular distance from pivot

Question 10

work done by a force

Answer 10

force x distance moved in the direction of the force.

Question 11

power

Answer 11

the rate of work done

Question 12

force constant of a spring

Answer 12

force per unit extension

Question 13

scalar

Answer 13

a quantity with magnitude only

Question 14

vector

Answer 14

a quantity with both magnitude and direction

Question 15

terminal velocity

Answer 15

the velocity of a falling object when weight = drag.

Question 16

centre of gravity

Answer 16

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

Question 17

thinking distance

Answer 17

the distance travelled by the car in the time taken by the driver to react

Question 18

braking distance

Answer 18

the distance travelled by the car after the brakes are applied until the car stops.

Question 19

stopping distance

Answer 19

thinking distance + braking distance.

Question 20

principle of conservation of energy

Answer 20

Energy cannot be created or destroyed; it can only be transferred into other forms.

Question 21

principle of moments

Answer 21

For an object in equilibrium, the sum of the clockwise moments about a point = the sum of the anticlockwise moments about the same point.

Question 22

Hooke’s law

Answer 22

extension of a spring is proportional to the force applied (as long as the elastic limit is not exceeded).

Question 23

stress

Answer 23

Force/Area

Question 24

strain

Answer 24

Extension/original length

Question 25

Young modulus

Answer 25

Stress/strain

Question 26

ultimate tensile strength

Answer 26

the breaking stress of a material

Question 27

elastic deformation

Answer 27

material returns to original shape when the force is removed.

Question 28

plastic deformation

Answer 28

material does not return to original shape when the force is removed.

Question 29

newton

Answer 29

The force which gives a mass of 1{kg} an acceleration of 1 {ms}^{-2}

Question 30

joule

Answer 30

The work done by a force of 1 {N} moving an object 1 {m} in the direction of the force.

Question 31

watt

Answer 31

The power transferred by one joule per second