Topic 8 - forces doing work Flashcards
Name the energy stores?
- Kinetic
- Thermal energy
- Electrostatic
- Elastic potential
- Magnetic
- Nuclear
- Gravitational potential
- Chemical
What is a system?
A single object or a group of objects that we are interested in
What happens when a system changes?
Energy is transferred between different objects/different energy stores. Some energy is also dissipated as heat and sound.
What is a closed system?
A system where the net change in energy is zero
Give an example of transferring energy by heating
e.g. With a camping stove and a pan of water, energy is transferred from chemical energy store of gas to thermal energy store of pan and water, increasing their temp
Give an example of transferring energy by forces doing work
e.g when a box is lifted, work is done against gravity which causes energy to be transferred to the box’s kinetic energy and gravitational potential energy
Give an example of transferring energy electrically
e.g. an electric toothbrush transfers energy electrically from the chemical energy store of the battery to the kinetic energy store of the bristles
What are 3 ways of transferring energy
- By Heating
- By forces doing work
- Electrically
What happens when a force moves an object through a distance?
Work is done and energy is transferred
What is the formula for work done?
Work done = force * distance
Why does a force doing work often cause a rise in temperature?
Because energy is often dissipated to the thermal energy store
How do you work out change in gravitational potential?
Change in GPE = mass (kg) * gravitational field strength (N/kg)* change in vertical height (m)
How do you calculate kinetic energy?
Kinetic energy = 1/2 * m * v squared
When do mechanical processes become wasteful?
When they cause a rise in temperature and energy is dissipated to the thermal energy store
Define power
The rate of energy transfer
