A **scalar quantity** has magnitude only. [tutorial]

A **vector** **quantity** has magnitude and direction. [tutorial]

**Displacement** is distance travelled in a specific direction.

**Velocity** is rate of change of displacement.

**Acceleration** is rate of change of velocity.

**Mass** is the property of a body that resists change in its motion.

**Density** = ^{mass}/_{volume}

1 **Newton** is the force that causes an object of mass 1 kg to accelerate at 1 ms^{-2}.

**Weight** is the effect of a gravitational field on a mass.

**Pressure** is the force per unit area.

**Moment** of a force about a pivot = Force × perpendicular distance between the line of the force and the pivot.

**Torque** of a couple = Fd (distance between lines of the forces is d and each force is F.)

The **principle of moments** states that for an object in equilibrium, the sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point.

The **centre of gravity** is the point through which the weight appears to act.

**Work** is force multiplied by distance moved in the direction of the force.

1 **joule** of work is done or 1 J of energy is transferred when a force of 1 N moves though a distance of 1 m.

The **principle of conservation of energy**: energy is neither created nor destroyed. It is converted from one form to another.

**Power** is the rate of doing work or the rate of converting energy.

1 **watt** is the power when 1 joule of work is done per second.

An object obeys **Hooke's law** if the extension is proportional to the load.

**Elastic behaviour** is when the sample returns to its original length when a load is removed.

**Plastic behaviour** is when the sample does not return to its original length when loads are removed.

**Stress** is force per unit area.

**Strain** is extension per unit length.

**Young modulus** is the ratio of ^{stress}/_{strain}.

**Ultimate tensile stress** (U.T.S.) is the maximum stress when the sample brakes.

Repeat this until you've completed the list and are happy. Come back to the same list and test yourself a week later. See how many you can remember!