3.3 Work, energy, and power

• work done = force x distance moved in the direction of the force
• Units of work done are Nm or J
• 1J is the work done when a a force of 1N causes a movement of 1m in the direction of the force
• Work done is when an object is lifted off the ground as kinetic energy is transferred to GPE as the object is lifted
• Energy is defined as the capacity to do work
• when an object is on an inclined plane, the distance is the vertical change in height of the object as the work done against the force of gravity is tranferred to GPE
• Kinetic energy= $0.5mv^2$
• efficiency = useful output energy/ total input energy x 100
• High efficiency means little energy is dissipated
• Power is the rate of work done
• Power = work done / time
• Moving an object along a non-smooth plane requires a constant force to be applied to maintain a constant speed as friction will always act on the object so work done by the forward force has to be equal to the frictional forces working against it
• GPE is the capacity for doing work as a result of an object's position in a gravitational field
• kinetic energy is the energy associated with an object as a result of its motion
• kinetic energy is directly proportional to mass and inversely proportional to velocity squared
• mechanical energy is the energy possessed by an object due to its position or movement
• the total energy of a closed system remains constant : energy cannot be created or destroyed due to the conservation of energy