Physics- key stuff
- Created by: Splash Heslin
- Created on: 11-05-15 14:52
Distance- time graphs
- The steeper the gradient, the faster the speed.
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- Straight line= constant speed.
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- Flat horizontal= standing still
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- Curved = acceleration
Velocity graphs
- Straight line= acceleration
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- Flat horrizontal= constant speed
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- Distance travelled = area under graph
Force
- Units for force: N
Momentum
mom= m x v
- Momentum is a vector.
- -------------------------------------------------------------
- Unit for momentum= kgm/s
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Explosions:
Mom before = mom after
Stopping Distance
Reaction time: how long it takes to see someting, process it, and react.
Thinking distance:the distance moved (in car) when you are processing something (dog in road).
Breaking distance: the distance travelled once you have hit the breaks.
stopping distance= thinking + breaking
Factors affecting stopping distance stuff
Factors affecting reaction time:
- drugs
- tiredness
- age
- drunkness
Factors affecting breaking distance:
- condition of car
- condition of road
- massof car
- speed of car
Hooke's Law- Extention
Extention= new length - orginal length
- force= mass x gravity
- gravity= 10
- curve on top of line graph is the elastic limit!
spring constant= Force / extention
Terminal velocity
Terminal velocity:
- 0 resulutant force
- 0 acceleration
- costant speed
Faster= more air resistance
- Eventually, all energy is used up to overcome air resistance.
- =forces are balanced when object is falling.
Energy
Work done= force x distance moved
Units for energy: joules
Power = work done / time taken
1 watt = 1J / 1s
EP= m x g x h Gravitational potential
EK= 1/2 mv Kinetic
Moments
Moment- turning effect of a force (pivot)
moment of force= force x perpendicular distance from pivot
- Moments have a direction
- .
- Centre of mass: point where an object's mass is
.thought to act through
- wide base = more stable
- lower centre of mass = more stable
Circular motion + pressure
Circular motion:
- Velocity has a direction, as is changeing. If velocity changes, there must be an accelaration. Therefore, an object going at the same speed can be accelerating (in a circle)
- Centripetial force: force acting towards centre of mass.
- .
Pressure:
pressure= force / area
Lenses
Convex/ converging: forms a real image.
Concave/ diverging: forms a virtual image.
Lense Formula: 1 + 1 = 1 u v f
Magnification: image height object height
Power of Lense: 1 focal length
The eye
Short sight: light focuses too quickly. Only see close objects clearly.
correction: diverging lense.
Long sight: light focuses behind retina. Only distant objects clearly.
correction: converging lense.
Electric current
If an object looses electons it becomes positive
If an object gains electrons it becomes negative.
Ion: a charged atom
Electric current: a flow of charge. Measured by an ammeter. AMPS
Battery: two or more cells connected together.
current= charge flow time taken
Potential Difference
Potential Difference: Voltage = potential difference
A mearure of energy transferreent across a component
Meassured by volt meter. VOLTS.
potential difference= energy transferred charge
Resistance: ions resit the passage of electrons
Measured in : ohms
resistance= potential difference Larger resistance= smallercurrent current
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