revision notes for 20th jan 2010

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• Created on: 28-12-09 14:35

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_PHYSICS

*Forces and Motion

*Electricty

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forces ane motion

Forces and Motion

• Velocity and Acceleration
• D-T and V-T graphs
• Mass, Weight and Gravity
• The three Laws of Motion
• Friction forces and Terminal speed
• Stopping Distances
• Momentum and Collisions
• Car Safety
• Work and Potential Energy
• Roller Coasters
• Power
• Fuels for Cars
• Revision Summary
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Velocity and Acceleration

Speed and Velocity are both how fast you'r going. Both measured in m/s (mph or km/h).

*speed is just how fast you're going (e.g. 30 mph or 20 m/s) with no regard to the direction. Velocity however must also have the direction specified, e.g. 30 mph north or 20 m/s, 060'.

Speed, distance and Time- the formula:

• Speed= distance/time
• Example: a cat skulks 20m in 35s, find a) it's speed b) how long it takes to skulk 75m.
• answer: using the formula triangle: a) s=d/t = 20/35= 0.57 m/s
• b) t=d/s = 75/0.57= 131 s= 2 mins 11 sec
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Velocity and Acceleration

Acceleration is how quickly you speed up. (how quick the velocity is changing) measured in m/s2.

acceleration- the formula:

• acceleration= change in velocity/time taken
• example: a cat accelerates steadily from 2 m/s to 6 m/s in 5.6 s. find its acceleration.
• answer: using the formula triangle a= v/t = (6-2) / 5.6= 4/ 5.6= 0.71 m/s2
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D-T and V-T Graphs

Distance time graphs

• flat sections are where it's stopped
• the stepper the graph, the faster it's going.
• downhil sectrions mean it's going back to it's starting point
• curves represent acceleration
• a steepening curve means it's speeding up
• a leveling off curve means it's slowing down

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D-T and V-T Graphs

velocity- time graphs

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