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
    • 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
    • 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
    • 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


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