P4 Keywords

Substances that conduct heat (allow heat to pass through them) very well -conductors of heat

Ratio of the useful work done by a machine to the total energy input, often written as a percentage.-efficiency

A push or a pull, measured in Newtons (N)- force (F)

The force that resists when you try to move something. The direction of the friction force is always in the opposite direction to the motion.-friction

The force of gravity on a mass of one kilogram. The unit is Newtons per kilogram. The value of g on Earth is 10N/kg-gravitational field strength (g)

Objects have more gravitational potential energy when they are higher up in the Earth's gravitational field. GPE = mgh-gravitational potential energy (GPE)

Substances that do not conduct heat very well-insulators of heat-insulators of heat

The unit of energy. One joule is the energy transferred if we push an object with a 1 Newton force for 1 metre. 1 J = 1 Nm.-Joule (J)

Moving objects have kinetic energy. Fast, massive objects have more kinetic energy than slow, light objects KE = ½ m v2-kinetic energy (KE)

Energy cannot be created or destroyed. Also known as “The Principle of Conservation of Energy”-law of energy, first

Some energy always becomes unusable whenever energy is transferred. Shown by the fact that some energy is always wasted as heat during an energy transfer-law of energy, second

Amount of energy transferred every second. The energy can be transferred from somewhere (e.g. a power station) or to somewhere (e.g. an electric kettle). Power = energy transferred / time taken. P = E / t.-Power (P)

Force of gravity on a mass. W = m x g. The unit of weight is the Newton.-Weight (W)

Energy transferred when a job is done. Work = force x distance moved in direction of force. Wd = F x d.-Work (Wd or E)