# GCSE OCR B Gateway Science Physics P5 Revison Notes

I had to make these for homework, condensed notes on p5, i hope they are helpful :-)

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• Created by: Amy
• Created on: 16-06-11 21:35

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P5
Gravity and Circular Motion
The two types of satellite are natural and artificial
Artificial ­ Navigation, spy, military, weather, communications
Natural ­ The Moon
Geo stationery
Satellites orbit with the same period as the earth
36000km above the equator
so from the surface of the Earth their position appear fixed
Polar stationery
Satellites orbit around the poles, whilst the Earth spins
underneath, allowing large areas of Earth to be seen
The orbital period is small
Speed formulas
Speed = Distance ÷ Time
S =d/t
Speed measured in metres per second (m/s)
Distance measured in metres (m)
Time measured in seconds (s)
Satellite orbit
Speed = Circumference of Circle ÷ Orbital Period
S = (2r) / T
Speed measured in metres per second (m/s)
Orbital Period measured in seconds (s)
Circumference measured in metres (m)
Planets in orbit
Gravity keeps them moving in a circle like a string keeps a bung rotating
We call the force that keeps an object `orbiting' a centripetal force
What provides the centripetal force for:
Planets
The bung
Comets
Non-Luminous irregular lumps of rock or ice/dust mix
They are tiny
They orbit the Sun
The earth
The Earth orbits the sun every year (365 1/4 days)
This orbit is actually a "slightly squashed" circle (ellipse)
The Earth is kept in orbit by the force of Gravity

## Other pages in this set

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Gravity also keeps the moon in orbit around the Earth
The moon orbits the Earth every month (28 days)
Vectors and Equations of Motion
Vectors have magnitude and direction
Scalars only have magnitude
Scalars
Distance
Speed
Mass
Energy
Density
Vectors
Displacement
Velocity
Acceleration
Force
Momentum
Constant velocity
Velocity=distance/time
V=s/t
If Velocity is not constant , this equation just gives the average velocity for the journey
DISTANCE = VELOCITY x TIME
S=VT
UNIFORM ACCELERATION
s = DISTANCE TRAVELLED
u = INITIAL VELOCITY

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If they meet each other exactly in phase, the amplitudes `add up' to produce large crests and
troughs.
Destructive interference
If two waves meet each other exactly out of phase
The amplitudes `subtract' to produce no peaks or crests.
Young slits
To get two waves of light to interfere, the waves must be very similar.…read more

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Time is measured in seconds (s).
Force is measured in newtons (N).
Ripple tank
A ripple tank is a device used to study the behaviour of waves, because all waves behave in
a similar manner.
A ripple tank produces water waves that can be reflected, refracted and diffracted.
Reflection and refraction
If it is a plane barrier then the waves are reflected.
The change in depth of the water causes a change in speed of the waves ­ they are

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Different types of radio waves are used to transmit signals for radio, TV, mobile phones,
Wi-Fi and satellite communications
In a transmitter, sound waves are turned into oscillating current