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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)

4.3 Understand that energy is conserved

4.2 what does potential mean

energy transfers involving the following forms of energy: thermal (heat), light, electrical, sound, kinetic, chemical, nuclear and potential (elastic and gravitational)

Potential  means stored energy.

Scientific Facts I need to remember to improve

3.19 Experiment to determine the refractive index of glass, using a glass block

3.17 Investigate the refraction of light, using rectangular, semicicular blocks and triangular prisms

3.16 Plane mirrors

For plane mirrors, the image would be.....

• The same size as the object.
• The same distance as the object from the mirror.
• Virtual (not real).
• Upright.
• Laterally inverted.

3.15 Light waves are transverse waves which can be reflected, refracted and diffracted

Angle of incidence i	Angle of reflection r
10o	10o
20o	20o
30o	30o
40o	40o
50o	50o

Formula: i = r

3.13 Effects of excessive exposure of the human body to electromagnetic waves

• Microwaves- Internal heating of body tissue.
• Infrared- Skin burns.
• Ultraviolet- Damage to surface cells and blindness.
• Gamma rays- Cancer, mutation.

3.12 Electromagnetic Uses

• Radio waves- Broadcasting and communications.
• Microwaves- Cooking and satellite transmission.
• Infrared- Heaters and nigh vision equipment.
• Visible light- Optical fibres and photography.
• Ultraviolet- Fluorescent lamps.
• X-rays- Observing the internal structure of objects and materials and medicals applications.
• Gamma rays- Sterilising food and medical equipment.