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13 Cards in this Set
- Front
- Back
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What is 'work done'? |
When an object is moved by a force, energy is transferred and work is done. But work is not a form of energy - it is one of the ways in which energy can be transferred. Work done and energy transferred are measured in joules (J). The work done on an object can be calculated if the force and distance moved are known. |
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When does a change in momentum occur? |
A change in momentum happens when a force is applied to an object that is moving or is able to move. The total momentum in an explosion or collision stays the same. |
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What is the equation for work done? |
work done (joule, J) = force (newton, N) × distance (metre, m) |
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What is gravitational potential energy? |
Any object that is raised against the force of gravity stores gravitational potential energy. For example, if you lift a book up onto a shelf, you have to do work against the force of gravity. The book has gained gravitational potential energy. |
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Formula for GPE? |
GPE (J) = mass (kg) x gravitational field strength (or 'g') (N/kg) x height (m) |
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What is elastic potential energy? |
Elastic objects such as elastic bands and squash balls can change their shape. They can be stretched or squashed, but energy is needed to change their shape. This energy is stored in the stretched or squashed object as elastic potential energy. |
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What is kinetic energy? |
Every moving object has kinetic energy (sometimes called movement energy). The more mass an object has, and the faster it is moving, the more kinetic energy it has. You should be able to discuss the transformation of kinetic energy to other forms of energy. |
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Formula for KE? |
kinetic energy = 1⁄2 × mass × speed2 |
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What is momentum? |
A moving object has momentum. This is the tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum. |
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Formula for momentum? |
momentum (kg m/s) = mass (kg) × velocity (m/s) |
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What is the conservation of momentum? |
So long as no external forces are acting on the objects involved, the total momentum stays the same in explosions and collisions. We say that momentum is conserved. You can use this idea to work out the mass, velocity or momentum of an object in an explosion or collision. |
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Explain what the safety features in car are for. |
When there is a car crash, the car, its contents, and the passengers, decelerate rapidly. They experience great forces because of the change in momentum, which can cause injury. If the time taken for the change in momentum on the body is increased, the forces on the body are reduced too. Seat belts and crumple zones are designed to reduce the forces on the body if there is a collision. |
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Formula relating change in momentum and force? |
Force = change in momentum/ time taken for change |
