Forces

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  • Created by: Clare
  • Created on: 24-10-12 18:59
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  • Forces and Motion
    • Velocity
      • Terminal Velocity
        • Mass and air resistance are balanced
        • Zero resultant force
        • Sky diver
          • As they fall they speed up.
            • More air resistance= less acceleration
              • Force from drag balances due to gravity(terminal velocity)
                • Parachute opens, increased air resistance
                  • Eventually rebalances at a much lower terminal velocity
        • Opposing forces are balanced so there is a constant velocity
        • Affected by: Weight, Surface area, Amount of force
      • Speed in a given direction
      • m/s
    • Resultant Force
      • SUM of all forces acting on a body
      • Objects going the same way
        • ADD to find resultant force
      • Objects pulling away from each other
        • SUBTRACT
      • Stationary
        • Zero forces
      • Constant Velocity
        • Balanced forces
      • Acceleration
        • Unbalanced forces towards direction of motion
      • Decceleration
        • Unbalanced forces against direction of motion
      • Mass x Acceleration
    • Acceleration
      • Acceleration= change in velocity / time
      • Change in velocity= final- initial value
      • Deceleration= negative
    • Speed
      • Stopping distance
        • Thinking + Braking
          • Thinking- reaction time
            • Affected by: Drugs, Tiredness, Age, Distractions, SPEED
          • Braking- distance between hitting brakes and stopping
            • Affected by: Road surface, quality of brakes and tyres, SPEED
        • Distance taken for moving object to stop
      • Distance/ Time graph
        • Horizontal= stopped
        • Straight line= constant speed
        • Gradient= velocity (upness/ alongness)
          • Steeper= faster
      • Speed= Distance/ Time
    • Momentum
      • Momentum BEFORE= Momentum AFTER
        • Conservation of momentum
        • IF no other forces are acting
      • Momentum= Mass x Velocity
        • Velocity= m/s
        • Mass= kg
        • Momentum= kg m/s
      • Add total momentum before collision
        • Rearrange knowing momentum after to find missing vaue
    • Moments
      • Moments make things turn or rotate around a point
      • Moments= Distance from pivot x Mass
        • Lift more weight= more distance between pivot and force
      • Have direction- clockwise or anticlockwise
      • Measured in Nm (Newton Metres)
      • Fixed point- pivot or fulcrum
    • Mass, Weight, Gravity
      • Mass: amount of matter in the object
        • Different per object but doesn't change from earth to moon
      • Weight: force of gravity acting
        • On earth stays the SAME
      • Gravity: field created by any object with mass
        • 10N per kg Towards the centre of the earth
      • ALL objects fall at the same speed due to gravity always acting
        • On earth: objects with a larger surface area fall slower due to air resistance
      • Mass= weight            gravity

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