G481 Difinitions

Question 0

Vector

Answer 0

A quantity that has magnitude (size) and direction.

Question 1

Scalar

Answer 1

A quantity that has magnitude (size), but no direction.

Question 2

Displacement

Answer 2

Distance moved in a particular direction from the starting point.

Question 3

Instantaneous speed

Answer 3

Rate of change of distance.

Question 4

Average speed

Answer 4

Total distance/time.

Question 5

Velocity

Answer 5

Rate of change of displacement.

Question 6

Acceleration

Answer 6

Rate of change of velocity.

Question 7

Terminal velocity

Answer 7

Constant velocity reached when an object falls under gravity. The presence of drag forces and resultant force = 0.

Question 8

Weight

Answer 8

Mass X gravitational field strength.

Question 9

Centre of mass

Answer 9

The point at which the mass of a body appears to be concentrated (or the point from which the weight of a body appears to act).

Question 10

Newton

Answer 10

1N is the force that gives 1kg of mass of an acceleration of 1ms-1.

Question 11

Moment of force

Answer 11

Force X perpendicular distance of force from pivot.

Question 12

Principle of moments

Answer 12

When a body is in equilibrium, resultant moment = 0 (sum of CW moments = sum of ACW moments about a point).

Question 13

Couple

Answer 13

Two equal and opposite forces.

Question 14

Torque of a couple

Answer 14

One of the forces X perpendicular separation of the forces.

Question 15

Which two conditions are necessary for equilibrium?

Answer 15

1. Resultant force = 0 in any direction

2. Resultant moment = 0 about any point

Question 16

Density

Answer 16

Mass/Volume

Question 17

Pressure

Answer 17

Force/Area

Question 18

Thinking distance

Answer 18

Distance travelled between the driver seeing the hazard and applying his brakes.

Question 19

Braking distance

Answer 19

Distance travelled between the driver applying his brakes and stopping.

Question 20

Stopping distance

Answer 20

Total distance travelled from seeing the hazard to stopping (or thinking distance plus stopping distance).

Question 21

Work done

Answer 21

Force X distance moved in the direction of the force

Question 22

The principle of energy conservation

Answer 22

Energy can not be created or destroyed, just changed from one form into another.

Question 23

The Joule

Answer 23

1J is the energy enquired to move a weight of 1N (through) a distance of 1m.

Question 24

Power

Answer 24

Rate of doing work
(or work done/time)
( or energy transferred/time)

Question 25

The Watt

Answer 25

The power required to move 1N through a distance of 1m in 1s.

Question 26

Stress

Answer 26

Stress = force/cross-sectional area

Question 27

Strain

Answer 27

Strain = extension/original length

Question 28

Young’s modulus

Answer 28

Young modulus = stress/strain

Question 29

Ultimate tensile strength

Answer 29

Maximum stress a material can withstand (before it breaks)

Question 30

Elastic deformation

Answer 30

Material returns to original length when the force is removed.

Question 31

Plastic deformation

Answer 31

Material does not return to original length when the force is removed.

Question 32

Hooke’s Law

Answer 32

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