# P2

physics exam 2

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## velocity and acceleration

Speed and Velocity both how fast you are going

distance = speed x time

Acceleration is how quick you speed up

change in velocity = acceleration x time taken

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## d-t and v-t

DT                                              VT

flat = stopped                          flat = steady speed

downhill = going back             uphill = acceleration

curves = acceleration             downhill = deceleration

area under = distance travelled

curve = change in acceleration

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## mass and weight and gravity

Gravity is the force of attraction between all masses

on earth's surface makes things accelerate (10m/s2)

gives everything a weight

makes things orbit

Mass = amount of stuff in an object (same anywhere) kg

Weight = force of gravity (changes) N

W = m x g

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## the laws of motion

First Law. balanced forces mean no change in velocity

Second Law. a resultant force means acceleration

f = ma

Third Law. if object A exerts a horce on object B then object B  exerts the exact opposite force on object A

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## drag and terminal velocity

Steady Speed - Driving Force  = Frictional Force

drag increases as speed increases

resistance is reduced when more stream lined

Falling Objects

Accelerate until resistant force = Accelerating force

Terminal Velocity depends on shape and area

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## stopping distances

Stopping Distance = Thinking Distance + Braking Distance

Thinking  - tiredness, drugs, alcohol, age, surrondings

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## work done

Means energy transferred (J)

When work is done energy is used this energy is the work done

Work Done is the wasted and useful energy

work done = force x distance

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## kinetic and potential energy

Kinetic Energy is Movement Energy

kinetic energy = 1/2 x mass x velocity2

Stopping distance increases alarmingly with extra speed because the velocity is squared

Potential energy is stored energy

Springs have it, it is releases as KE

Higher an object more gravitational potential energy

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## momentum and collisions

momentum = mass x velocity

momentum has size and direction

momentum before = momentum after

change in mo = force acting x time taken

crumple zones increase time taken

seat belts increase time taken

air bags increase time taken

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