S1/2 Forces and Space

Galaxy

is a huge cluster of stars and planetary systems held together by gravity.

Goldilocks zone

area around a star which has the right conditions for life.

Moon

natural satellite that orbits a planet.

Planet

mass of rock or gas that orbits a star.

Satellite

any object orbiting around another. It could be natural (a moon) or artificial.

Solar system

planetary system that orbits (circles) a central star.

Star

large ball of matter (usually hydrogen and helium) that emits light.

Universe

all matter in existence.

Balanced forces

forces acting on an object are equal in size and opposite in direction.

Force

push or pull which can alter the speed, shape or direction of an object.

Newtons

Units for measuring a force.

Newton balance

equipment used to measure a force.

Unbalanced force

When the forces acting on an object are not equal in size or opposite in direction.

Gravity

the pull of an object towards a large mass e.g. planet

Mass

how much matter there is in an object and is measured in kilograms (kg).

Weight

the force (downwards pull) caused by gravity

Aerodynamic

a shape which reduces air resistance (drag).

Air resistance

friction produced when an object moves through air.

Friction

force produced when two surfaces rub together (friction always opposes the direction of motion).

Lubricate

reducing friction between two surfaces e.g. using oil.

Streamlined

shape reducing resistance and therefore the force of friction.

Water Resistance

friction produced when an object moves through water.

Acceleration

rate of change of speed measured in metres per second per second (m/s²).

Average speed

distance travelled divided by the time.

Instantaneous speed

speed an object is moving at one moment in time (eg speedometer in a car)

Speed

rate of change of distance measured in metres per second (m/s).