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