# 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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