P8 Forces doing work

When a force causes an object to move through distance work is done on the object. So a force does work on an object when the force causes displacement of the object

Work done is measured in jules

equation for work done is force * distance moved in the direction of the force

When an object is raised above ground level it gains GPE.

GPE stored energy can be lost if object is allowed to fall

THe equation for change in GPE

Change in GPE = Mass gravitational field strength change in height

Moving objects have kinetic energy

More kinetic energy = longer jump will be. Kinetic energy depends on mass and velocity

Equation for kinetic energy

Kinetic energy = 1/2 mass speed^2

when work is done against frictional forces on an object there is a temperature increase of the object

A bicycle bump gets hot in use as work done is compressing gas causing the pump to get hotter

Energy can be stored transferred and dissipated but energy cannot be destroyed or created

Compressing the air causing molecules to increase in their frequency of collisions causing frictional heating and an increase in temp

Power is the rate at which energy is transferred and is measured in jules per second

equation for power

work done/time taken

the amount of useful energy you get from an energy transfer compared to the total is called efficency