yr 8 physics

energy

the ability to do work

work

force and distance

formula to calculate work

work = force x distance

kinetic energy

the energy an object has due to its motion

potential energy

Energy that is stored and held

formula to calculate power

power = work/time

work unit of measurement

Joules (J)

energy unit of measurement

Joules (J)

formula to calculate force

mass x acceleration

power unit of measurement

Watts (W)

power

the rate at which work is done

power formula

work (J) / time (S)

time unit of measurement

seconds (s)

distance unit of measurement

meters (m)

force unit of measurement

Newtons (N)

acceleration of gravity

10m/s2

How many joules are in a kilojoule?

1000 joules

how many kilojoules in a megajoule

1000 kilojoules

how many joules in a megajoule

1,000,000 joules

joule to kilojoule conversion

Joule ÷ 1000

kilojoule to joule conversion

kilojoule × 1000

megajoule to joule conversion

megajoule × 1,000,000

joule to megajoule conversion

joule ÷ 1,000,000

megajoule to kilojoule conversion

megajoule × 1000

kilojoule to megajoule conversion

kilojoule ÷ 1000

gravitational potential energy

energy of an object stored in its position above the surface of the earth

chemical energy

a form of potential energy that is stored in chemical bonds between atoms.

nuclear energy

form of potential energy stored in the nucleus of an atom

elastic energy

the potential energy of an object that is stretched, compressed or bent

mechanical energy

a form of kinetic energy possessed by an object due to its motion

thermal energy

a form of kinetic energy due to the vibrations of atoms and molecules making up the substance

sound energy

the movement of energy through substances in longitudinal waves

light energy

movement of energy through electromagnetic field int he form of transverse wave

nuclear fusion

when 2 nuclei are smashed together

nuclear fission

when a nucleus is split into 2

forms of potential energy

elastic, chemical, gravitational, nuclear

forms of kinetic energy

sound, thermal (heat), light, electrical, mechanical

electrical energy

movement of electrons in one direction (a current)

nuclear energy

energy stored in the nucleus of an atom (binding energy)

nuclear reaction

a reaction that involves a change in the nucleus of an atom (release of energy)

how sound energy travels

sound energy is made by vibrations, which create sound waves

how light energy travels

as a transversal wave in a straight line
can travel through a vacuum, solid, liquid or gas

difference between heat and temperature

heat = specific form of energy that can leave or enter a system
temperature = average kinetic energy of particles

direction thermal energy moves in

from the warmer object to the colder object

conduction

the direct transfer of heat between objects in contact
heat transfers from the hotter object to the colder one
e.g. metal spoon in hot water

convection

process where heat flows through liquids and gases
causes heat to rise
e.g. spreading soup in a saucepan

radiation

heat spreads outwards from any hot object
e.g. heat of the sun outside

transparent

clear, allowing light to pass through

translucent

allowing light to pass through diffusely, not as clear

opaque

not letting light through

refraction

bending of light

reflection

bouncing back of a wave when it hits a surface through which it cannot pass

photoelectric effect

light acting as a particle to knock electrons out

light particle

photon

properties of light

1. travels much faster than sound
2. speed of light = 300 000km/s (approx.)
3. when it hits a surface, its either reflected, absorbed or transmitted
4. travels in straight lines
5. it can bend: refraction

dispersion

white light splitting into the rainbow due to refraction
e.g. rainbow, diamond, glass prism