Work done

• When objects  interact, the forces between them can lead to enrgy being transferred. 
• Sometimes the energy is stored in a useful form. 
• Sometimes energy is due to the speed of a moving object.
• The thermal energy content of an object may be increased. 

Work done by a force

• Work done = force x perpendicular distance moved in the direction of the force. 
• Forces occur in opposing pairs; so the force you exert to lift…