P5

Gravity is the force of attraction which acts between all masses.

The greater the mass, the greater the force of attraction.

The plants orbit the sun in near circular paths due to the gravitational force of attraction between the two bodies.

The planets are kept in orbit by:

• Gravity (centripetal force)
• Moving at a high velocity

The orbital period is the time taken to travel once around the Earth/Sun. 

Scalar Quantities - described by magnitude only.

Vector quantities - described by magnitude and direction.

Distance - S 

Time taken - T

Initial Velocity - U

Final Velocity - V

Acceleration - A

Projectile - any object that once dropped continues in motion.

The path of a projectile is called its trajectory.

A projectile on has gravity acting on it.

The horizontal velocity is constant.

The initial vertical velocity is zero and changes due to gravity. 

For every action there is an equal and opposite reaction.

A moving object has momentum.

Momentum = mass x velocity

Momentum is a vector quantity.(magnitude and direction)

Net momentum before = net momentum after

Diffraction is greatest when the wavelength is simliar in size to gap.

Radio waves have lower frequeny and longer wavelengths than Microwaves.

Radio waves are reflected by the ionosphere.

A wave that has been modified to carry a signal is said to have been modulated.

Long wave radio waves carry signals by amplitude modification.