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Force
- needed to change the velocity of an object
- rate of change of momentum
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Momentum
- mass x an objects velocity
- units: kgms-1vector quantity
- p=mv
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Newton's Laws of Motion
- First: an object remains at rest or in uniform motion unless acted on by a force
- Second: the rate of change of momentum of an object is proportional to the resultant force on it
- Third: when objects interact they exert equal and opposite forces on each other
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Force-time graphs
- the area under the line of a force-time graph represents the change of momentum or the impulse of the force
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Principle of Conservation of Momentum
- For a system of interacting objects, the total momentum remains constant, provided no external forces acts on the system
- mBvB + mAvA = mAuA + mBuB(mB + mA)V = mAuA + mBuB
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Elastic and Inelastic Collisions
- Elastic: one where there is no loss of kinetic energy, e.g. bouncy ball
- Totally Inelastic: one where the colliding objects stick together, e.g. car crash
- Partially Inelastic: one where the colliding objects move apart and have less kinetic energy after the collision than before
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Explosions
- mBvB = -mAvAmove apart in opposite directions
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