Force and Work

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When you push a box across a floor, you will see that the work done is NOT against the weight of the . The work done is in the direction of the force, . This work is done against the force of .

Friction arises because even the smoothest of surfaces are if you look at them under a microscope.

Friction can be reduced by lubricating the surfaces with . PTFE and have very low friction, so they are very .

When work is done against friction, most of the energy is turned to . You can see this very clearly when a plane lands on a runway. You can see the coming from the tyres.