Gravitational Potential Energy

Study Notes

Energy is conserved and cannot be created or destroyed, only transferred between stores.
The total energy remains the same before and after any changes.

As an object is lifted, work is done against the force of gravity, and energy is stored in the gravitational potential energy store.
The higher the object, the more energy is stored in the gravitational potential energy store.
Energy in the gravitational potential energy store (Ep) = mass (m) x gravitational field strength (g) x height (h).
The unit of measurement for energy in the gravitational potential energy store is the joule (J).
On Earth, the gravitational field strength (g) is 9.8 N/kg.

The faster an object is traveling, the more energy there is in the kinetic energy store.
Speed is measured in m/s, and velocity is speed in a particular direction.
Energy in the kinetic energy store (Ek) = 0.5 x mass (m) x velocity² (v²).
The unit of measurement for the amount of energy in the kinetic energy store is the joule (J).
The kinetic energy store of an object increases as its velocity and mass increase.

Energy can be transferred between stores through mechanical work, electrical work, heating, and radiation.
In the home, energy can be transferred by:
- Mechanical work – when a force is applied to move an object over a distance.
- Electrical work – when charge flows (electricity).
- Heating – when there is a difference in temperatures.
- Radiation – when energy is transferred as a wave, for example as light or sound.

Appliances can transfer energy from one store to another, such as a washing machine that transfers energy from electrical work to the kinetic energy store of the motor.
The power rating of an appliance can be used to calculate the amount of energy transferred while it is being used.
A power rating of 100 watts means that 100 joules of energy are transferred each second.

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