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| Question | Answer |
| P3d - Work and Power | . |
| Weight an Mass | Weight is not the same as mass. Mass is a measure of how much stuff is in an object. Weight is a force acting on that stuff. Weight is the result of gravity. |
| Calculating Weight | weight = mass × gravitational field strength - Weight is measured in newtons, N - Mass is measured in kilograms, kg - The gravitational field strength is measured in newtons per kilogram, N/kg For example, the gravitational field strength is: 10 N/kg on Earth 1.6 N/kg on the Moon |
| Work is done when a force moves an object in the direction in which the force acts. | The formula for work done: Work Done = Force x Distance Moved (in the direction of the force) Work done is measured in joules, J Force is measured in newtons, N Distance is measured in metres, m |
| Worked Example | If a person weighs 700N, the work he does against gravity when he jumps 0.8m is: Work done = 700 x 0.8 = 560J |
| Power | Power is the rate at which work is done. Power = work done ÷ time taken Work done = power x time Time taken = work done ÷ power Power is measured in watts, W Work done is measured in joules, J Time is measured in seconds, s |
| Cars | Some cars are more powerful than others. The power rating of a car depends on its engine size. More powerful cars have greater fuel consumption. |
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