Forces

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  • Created by: Holly45
  • Created on: 10-03-15 18:58

Forces between objects

  • when 2 objects push or pull on each other they exert equal and opposite forces on one another
  • unit of force is NEWTON (N)
  • friction
  • motive force
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Resultant forces

  • when the resultant force on an object is zero, the object remains stationary or continues to move in the same direction and speed
  • the resultant force is equal to the sum of the two forces and acts in the same direction as the 2 forces
  • if an object is acted on by 2 unequal forces acting in different directions, the resultant force is equal to the difference between the 2 forces and in the direction of the larger force
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Force and acceleration

  • F = M x A
  • if the velocity of an object changes, it must be acted on by a resultant force
  • the velocity of the object decreases if the resultant force is opposite in direction to its velocity
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On the road

  • breaking force needed depends on the speed of the vehicle when the brakes were applied and the mass
  • R = M x A : resultant force
  • the thinking distance is the distance travelled by the vehicle in the time is takes the driver to react
  • stopping distance = thinking distance + breaking distance

Factors affecting it:

  • the faster the vehicle is travelling
  • tiredness, drugs and alcohol
  • road conditions
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Falling objects

  • the weight of an object is the force of gravity on it
  • the mass of an object is the quantity of matter on it
  • weight = mass X gravitational field strength
  • the object reaches a constant velocity when the drag force on it is equal and opposite to its weight. This is terminal velocity
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Hooke's law

  • Force applied = spring constant X extension
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