Ch - 8 (Work & Power) Flashcards
What is work? (In simple words)
Transfer of energy due to force
What is power? (In simple words)
Rate of transfer of energy (work done per unit time)
What is efficiency? (in simple words)
Ratio of useful output and total input
What is work done in simple words?
Amount of energy transferred
What is the formula for Work?
Work = F x d
E (Energy) = F x d (force exerted in the direction of a force)
Unit: Joules
What is the formula for power?
Power = Work (Energy)/Time
Unit: Watts (W)
Define work done.
- the amount of energy transferred when one body exerts a force on another the energy transferred by a force when it moves.
- Work done = energy transferred
What are the factors affecting the amount of energy transferred by a force?
- Size - The greater the force, the more work it does.
- Distance moved in the direction of the force - the further it moves, the more work it does.
What is work done, measured in?
Joules (J)
1J = 1Nm
1000J = 1000 Nm
define power.
The rate at which energy is transferred or the rate at which work is done.
What are the important units of power?
- Watts (W)
1 W = 1 J/s
1000 W = 1kW
1000000 W = 1 MW
What is the relationship between work done and energy transferred.
Energy transferred (J) = Work done (J)
What happens when a force acts in the direction the object is moving in?
Gains energy (usually to its kinetic energy)
What happens when a force acts in the opposite direction the object is moving in?
Loses energy (thermal energy store of the surroundings i.e. dissipated as heat or thermal
What is one exam tip to remember?
- Always convert distance into metres
- Convert force into newtons
- Convertor done in joules
