32858446-AS-Edexcel-Physics-Revision - Mechanics Scalars...

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Mechanics Scalars and Vectors Scalars Vectors Mass Force Temperature Acceleration Time Momentum Length/distance Displacement Speed Velocity Energy Motion with constant acceleration Acceleration could mean change in direction, speed or both Free Fall Only force acting on object in free fall is its weight Objects can have initial velocity in any direction and still undergo free fall as long as force providing initial velocity is no longer acting Measuring g: o measure height from bottom of ball bearing to trapdoor o flick switch to simultaneously start timer and disconnect electromagnet, releasing ball bearing o ball bearing falls, knocking trapdoor down and breaking circuit, stopping timer Displacement-time graphs Gradient = velocity Straight line means constant velocity Curved line = acceleration Decreasing gradient = deceleration Velocity-time graphs Gradient = acceleration Area under graph = displacement Can be negative to show opposite motion Increasing gradient = increasing acceleration Decreasing gradient = decreasing acceleration Ultrasound position detector (data-logger) – more accurate (no human reaction times), higher sampling rate than humans, see data displayed in real time Mass, Weight and Centre of Gravity The greater an object’s mass, the greater its resistance to a change in velocity (inertia) Centre of gravity – single point that you can consider whole weight to act through (whatever its orientation) Object always balances around this point, even though sometimes CofG can fall outside object Object stable if low centre of gravity and wide base area
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Object will topple over if vertical line drawn downwards from centre of gravity falls outside base area Forces Free-body force diagrams show all forces acting on a single body Newton’s Laws of Motion 1 st law = A body at rest will stay at rest, a body in motion will continue to move in a straight line at a constant velocity, unless acted upon by a resultant external force 2 nd law = For a body of constant mass, the force applied is proportional to the acceleration 3 rd law = If body A exerts a force on body B, body B exerts an equal and opposite force on body A Newton’s 3 rd law pairs – same type of force Work and Power Work is the amount of energy transferred from one form to another when a force causes a movement of some sort 1 joule is the work done when a force of 1 newton moves an object through a distance of 1 metre Power is rate of doing work – amount of energy transformed from one form to another per second Power = work done / time Watt is defined as rate of energy transfer equal to 1 J/s Power = force x velocity Conservation of Energy Efficiency = useful power output / power input Materials Hooke’s Law If you increase the load past the elastic limit, the material is permanently stretched Elastic deformation – material returns to original shape when forces are
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This note was uploaded on 09/07/2011 for the course RANDOM R 101 taught by Professor T.s. during the Fall '11 term at Research College.

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32858446-AS-Edexcel-Physics-Revision - Mechanics Scalars...

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