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PHYSICS - Coggle Diagram
PHYSICS
FORCES
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Vector
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- if no resultant force, no acceleration
Weight
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if holding an object of lifting it a a constant speed, you must be pushing upwards with a force that's the same size as its weight.
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Moments
when the sum of clockwise moments = sum of anticlockwise moments, a system is in equilibrium.
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NEWTONS'S LAWS OF MOTION
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3RD
For every action (force), there is an equal and opposite reaction (force) (this is not balanced forces).
1ST
If no resultant force acts on an object, its motion will be constant (velocity will not change)
Stopping distances
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Braking distance
- condition of brakes, tyres and road
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- speed (braking distance x4)
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Momentum
In any collision, total momentum is always conserved
longer the time over which momentum is lost or gained, the lower the force exerted, and vice versa.
WAVES
TRANSVERSE
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e.g. water waves, seismic S waves, light, EM waves
LONGITUDINAL
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e.g. sound, seismic P waves
sound waves cause eardrum to vibrate, which sends a signal to the brain.
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when sound meets a boundary between two mediums (materials), some sound is transmitted, while some is reflected. Resulting echoes can be timed to build up a image of what's out of view e.g. a baby in a womb, or schools of fish underneath a boat (sonar).
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seismic P-waves (longitudinal) pass through the centre of the Earth while S-waves (transverse) do not suggests that it has a molten (liquid) core
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Refraction
If speed decreases, wavelength also does, while frequency stays constant.
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when waves enter a new medium (material), their speed changes, as does their angle.
Colour & Blackbodies
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if the rate of absorption is greater than the rate of emission, its temperature increases. But this then in turn increases the rate of emission.
SPACE PHYSICS
sun is orbited by 8 planets & their moons, and dwarf planets.
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LIFE CYCLE OF STARS
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when star is larger than our Sun - produces heavy elements, and new nebula.
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Satellites
their orbits are circular, which means that while their speed is constant, their velocity is always changing, due to their direction changing. It's accelerating, but not getting faster.
Used for GPS - TV - communications.
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Natural & artificial satellites orbit the earth. Geostationary satellites orbit above the same point of equator.
-if a satellite has an elliptical orbit, it gets closer to the earth, and vice verse.
used for reconnaissance & weather.
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ELCTRO / MAGNETISUM
Magnetism
permanent magnets always produce a magnetic field, whereas induced magnets become magnetised when in another magnetic field.
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Iron - Cobalt - Nickel are magnetic and so are attracted to permanent magnets. Other metals like aluminium and copper are not.
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Motors
use motor effect: both sides of a coil experience a force in opposite directions, and it turns.
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a split-ring commutator is needed to ensure that the current is reversed every half turn, in order to keep the coil spinning.
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LOUDSPEAKERS
also use the motor effect: a current is sent from a source e.g. phone - this causes the coil and speaker cone to vibrate, producing sound waves.
THE GENERATOR EFFECT
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To increase output:
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- turn faster: this requires energy though, due to the induced current producing its own opposing field
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MICROPHONE
an 'inverted loudspeaker. sound waver cause the coil to oscillate past magnet, which induces signal.
TRANSFORMERS
change the transmission voltage / p.d. through the national grid to reduce energy lost as heat due to resistance of cables.
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-A.C. input to primary coil induces alternating magnetic field in soft iron core -this induces a current in the secondary coil. -the side with the most turns has the greater p.d.. N & V are proportional, so x2 turns means x2 the p.d.
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