P10 - Forces + momentum
- Created by: Lucy Hart
- Created on: 19-01-20 20:14
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- P10 Force + Motion
- P10.1 Force and Acceleration
- RP - investigating force + acceleration
- resultant force = mass x acceleration
- Newton's 2nd law of motion
- greater mass of an object, the smaller acceleration (inversely proportional)
- greater the resultant force on an object, greater the object's acceleration (directly proportional)
- intertia - moving at constant velocity
- accelerates if the resultant force is the same direction as velocity
- decelerates if the resultant force is in opposite direction
- P10.2 Weight + Terminal Velocity
- weight - caused by gravitational force, newtons N
- mass - quantity of matter, kg
- weight = mass x g
- terminal velocity
- acceleration of an object decreases as it falls, frictional force increases, resultant force decreases so acceleration decreases
- terminal velocity - reaches constant velocity, frictional force on it is equal + opposite to its weight
- resultant force is zero
- weight - caused by gravitational force, newtons N
- P10.3 Forces + Braking
- stopping distance = thinking + braking
- thinking - distance travelled time taken for driver to react
- braking - distance travelled time the braking force acts
- factors affecting stopping distances
- tiredness, alcohol + drugs - increase reaction times
- faster a vehicle, further it travels
- wet + icy roads, have to brake with less force to avoid skidding
- worn brakes + tyres take longer to stop
- deceleration = v2 - u2 2s
- friction + air resistance oppose the driving force
- stopping distance = thinking + braking
- P10.4 Momentum
- momentum = kg m/s
- momentum = mass x velocity
- conservation of momentum - in a closed system, the total momentum before an event is equal to the momentum after the event
- P10.6 Impact Forces
- crumple zones - lessen force of impact
- the longer the impact time, the more the impact force is reduced
- reduced by soft pad, act as cushion, increase impact time, reduce momentum
- acceleration = change of velocity/time
- force = change of momentum/ time
- P10.7 Safety First
- cycle helmets + cushioned surfaces reduce impact forces by increasing impact time
- seat belts + air bags spread force so increase impact time
- side impact bars + crumple bars give way in an impact increasing impact time
- P10.5 Using Conservation of Momentum
- when two objects push each other apart, they move with different speeds if they are different masses but with equal + opposite momentum, so total momentum 0
- MaVa + MbVb = 0
- when two objects push each other apart, they move with different speeds if they are different masses but with equal + opposite momentum, so total momentum 0
- Untitled
- P10.8
- object is elastic if it returns to its original shape when forces are removed
- limit of proportionaliy - forces is too big, stretches more than predicted
- force = spring constant = extension
- extension of a spring is directly proportional to the force, as it doesn't exceed limit of proportionaliy
- P10.1 Force and Acceleration
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