Work, Energy & Momentum

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Work Done & Equations

  • In Physics, work is done whenever a force moves it's point of application in the forces direction
  • Energy Transferred = Work Done
  • 1 kg = 10N

Equations:

  • Work Done (J) = Force (N) x Distance moved in direction of the force (m)
  • Kinetic Energy (J) = 1/2 x mass (kg) x [velocity (m/s)]^2
  • G.P.E (J) = mass (kg) x grav. field strength (N/kg) x change in height (m)
  • Power (W) = Work done (J) / Time (s)
  • Momentum (kg.m/s) = mass (kg) x velocity (m/s)
  • F = ma
  • a = (v-u) / t
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Momentum & Explosions

  • A measure of the amount of motion in a direction
  • Total starting momentum = Total final momentum (providing no external force acts)

If two objects push away from each other:

  • Their speeds will be different if their weights are different
  • They will have equal and opposite momentums so their total momentum is 0
  • When vehicles collide, The force of the impact depends on mass, change in velocity and duration of the impact
  • The longer the impact force, the more the impact force is reduced

Vehicle Safety:

  • Seat belts and air bags are used to spread the force over the chest and increase the impact time
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