Hint
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Answer
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Momentum changes when
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A resultant force is acting
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Give Newton's 1st Law of motion
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An object will remain at rest of move at a constant velocity unless acted upon by a resultant force
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Give Newton's 2nd Law of motion
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Resultant force is equal to rate of change of momentum
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Give Newton's 3rd Law of motion
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When two objects interact they exert forces on each other that are equal in magnitude, opposite in direction, are of the same type and act along the same line.
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Define resultant force
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The vector sum of forces acting on an object
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Why does the acceleration of a rocket gradually increases during lift off
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Since the mass gradually decreases whilst the force is typically constant
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What is the same for two unequal masses hanging over a pulley
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The tension acting
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Give the equation for Momentum
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Mass × velocity
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Units equivalent to kgms⁻¹
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Ns
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Resultant force is equal to...(think N's 2nd Law)
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Equal to the rate of change of momentum
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Give the equation for Impulse
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Force × time
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What is shown by the Area under a force time graph
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Impulse
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What is shown by the Gradient of a momentum-time graph
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Resultant force
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Force × time
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Equal to change in momentum
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Conservation of momentum
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The total momentum in a system is constant provided no external force acts
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In an Elastic Collision....
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kinetic energy is conserved
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In an Inelastic collision
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kinetic energy is not conserved
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What is the law of conservation of energy
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Energy cannot be created or destroyed, ony transferred between objects and transformed between types
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Give the equation for Work done
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Force × displacement in the direction of the force
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Effect of friction on a moving object
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Transfers kinetic energy primarily to thermal energy
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Change in gravitational potential energy is equal to the change in kinetic energy is TRUE providing....
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If no resistive forces are acting
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Energy transferred is equivalent to
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Work done
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Give the equation for Efficiency
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Useful energy out ÷ Total energy in
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For an object sliding downhill at constant speed, Gravitational potential energy lost =
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work done by friction
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For a vehicle travelling uphill at constant speed, Work done by driving force =
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Gain in gravitational potential energy + work done by friction
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Define power
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Energy transferred per second
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Unit equivalent to Js⁻¹
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Watts
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For an object travelling at constant velocity under a driving force
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Power = Force × velocity
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On a force-distance graph the area under the line represent
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work done
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