low polar orbit - an orbit that goes directly over the poles
low earth orbit - satalites used for a close up veiw of earth
Geo stationary orbit - circles the earth at the same rate the earth is spinning, making it look still.
- gravitational forces are proportional to 1 over distance squared
- a centripetal force is needed to keep an object moving in a circle, the closer an object is to earth the faster its orbit
----- given on page 2 equation list
- t = time (s)
- s = displacement (m)
- u = intital velocity (m/s)
- v = final velocity (m/s)
- a = acceleration (m/s2) or gravity if object is falling = 10
Scalars & Vectors
Scalars - tell you how big something is -- magnitude only, examples; temeratures, speed, distance, mass
Vectors - have magnitude & a direction, examples; force, velocity, displacement
this means you can use pythagoras or trigonometry (if an angle is given) to find total velocity
- The trajectory of a projectile is parabolic (a curved path)
- for a projectile question you should draw a SUVAT table
Electromagnetic Waves & Satellites
electromagnetic waves that can pass through the atmosphere:
- radio waves
- infrared radiation
- visible light
- a signal is sent up to the satalite, where it is processed & retransmitted back to earth to another reciever. multiple Stalalites mean signals can travel further
- Due to microwaves having a shorter wavelength than radiowaves, they dont diffract as much, so dishs must be placed in straight lines as this is how microwaves travel.
- The size of the gap affects the diffraction of waves. If the gap is the same size as the wave length, then diffraction is at it's greatest.
- If two sound waves reinforce eachother to make a stronger sound, or they will cancel eachother out.
- If there is an even number of path difference, then the wave will constructive interfere.
Light... Particle or Wave?
evidence for light as a particle:
- travels in staright lines
- doesn't spread out (diffract), if it did shadows would be blurry (solar eclipse)
evidence light is a wave:
- light can be polarised proving its a transerse wave
- light can be defracted with a really short gap, due to it's short wavelength
- light can form an intereference pattern
polarisation- transverse waves can be plane polarisied meaning they are limmitted to one plane of ossilation instead of many. A polariod filter lets through light that is polarised in a certian plane.
Experiment to Show Interference
(past exam question)
- A transverse wave must be used, so you could use a ripple tank
- therfore wou will need two dippers in a water tank that produce waves of the same frequency
- you will get constructive & destructive interference
- when peaks and throughs meet constructive intereference occurs
- when waves meet and are not 'in phase' then destructive interference occurs
you may be asked to draw a diagram:
convex lenses & magnification
- magnification - where an image is magnified (appearing larger than the actual object)
- for an object to be magnified it must be between F (focal point) and 2F
- an object closer or less than F , then light defracts and no image is made
- a real image can be projected but a virtual image cannot
momentum - a product of mass and velocity (momentum = mass x velocity)
V= M1 U1 + M2 U2 / M1 + M2
- when a cricketer hits a ball, the action is the hit, the reaction is the ball flying forward and the bat flying backwards
- when hit the ball changes velocity as the force applied changes its momentum.
- a gun recoils beacuse it put a force on the bullet, while the bullet exerts a force on the gun, which is equal and opposite to the original force, causing the gun to recoil
- total momentum before collision = total momentum after collision -- due to the law of conservation of mass, however this only applies if no other force is acting up the objects (i.e. friction)