Scalar

A quantity that has Magnitude only without direction
Examples: Length, area, volume, distance, speed, mass, density, pressure, temperature, energy, work, power, electrical potential, charge, time.

Vector

A quantity that has (both) magnitude / size and direction
Examples: Displacement, velocity, acceleration, momentum, force (lift, drag, thrust, weight), field(s), a.c. voltage, current (when calculating fields only).

Displacement

(Net) distance moved in a particular direction.

Instantaneous speed

Speed measured between two point a very small time apart.

Average speed

Distance covered / time taken.

Velocity

Speed in a given direction  the rate of change of distance.

Acceleration

The rate of change of velocity/The gradient of a velocity vs time graph. (= change in velocity / time taken).

The Newton

The (net) force which gives a mass of 1kg an acceleration of 1 ms2.

Torque of a Couple

One of forces × perpendicular distance (between forces) (Not force x perpendicular distance).

Moment of a force

Moment = force x perpendicular distance from pivot / axis / point.

Thinking Distance

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

Braking Distance

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

Stopping Distance

Stopping distance: Thinking distance + braking distance.

Work done by a Force

Work done = force x distance moved / travelled in the direction of the force.

Joule

Energy required to move a weight of 1N (through) a distance of 1 m.

Power  rate of work done

Power = work (done)/time or power = energy/time or power = rate of work done.

Watt

Power required to move 1N through a distance of 1m in 1 sec (Rate of doing work).

Stress

Force/(crosssectional) area.

Strain

Extension/original length.

Young's Modulus

Stress/strain.
Young modulus is equal to the gradient from stressstrain graph (in the linear region).

Ultimate Tensile Strength (UTS)

Ultimate tensile strength = Maximum stress material can withstand (before fracture).

Elastic Deformation

Extension (or compression) force (as long as elastic limit is not exceeded).

Plastic Deformation

Material does not return to original length / shape/ size (is permanently deformed / longer) when the force / stress is removed.

Density

Mass/volume or mass per (unit) volume.
