Conservation of energy

How it is used

One of the most used principles in problem solving. Students write 'by conservation of energy...' and set the energy at the start equal to the energy at the end. Also called the law or principle of conservation of energy.

Example sentences

1. By conservation of energy, the speed of the pendulum bob at the bottom is √(2gh).

2. Conservation of energy tells us that the 'lost' energy has gone into heating the brakes.

Common collocations

• by conservation of energy
• law of conservation of energy
• apply conservation of energy
• energy is conserved

Related terms

• energyThe ability of a system to do work or cause change. It comes in many forms, such as kinetic, potential, thermal and chemical, and it is measured in joules (J).
• kinetic energyThe energy an object has because it is moving. It depends on mass and speed and equals one half times mass times speed squared (½mv²).
• potential energyEnergy stored in an object because of its position or condition, for example a raised book or a stretched spring. Near the Earth's surface, gravitational potential energy equals mgh.
• first law of thermodynamicsThe principle that the change in a system's internal energy equals the heat supplied to it minus the work it does. It is the conservation of energy applied to heat and work.
• conservation of momentumThe principle that the total momentum of a system stays constant if no external force acts on it. The momentum before a collision or explosion equals the momentum after it.

More terms: Energy, Work and Momentum

• work
• power
• momentum
• impulse
• elastic collision
• efficiency