Anouk does 150 J of work using a hammer to pull a nail out of a piece of wood, and the hammer does 105 J of work on the nail. What is the efficiency of the hammer?

The efficiency of any machine is given by:

efficiency = output obtained / input given

Substituting the values,

Efficiency = 105 / 150

Efficiency = 0.7

Converting this to a percentage, the efficiency of the hammer is 70%.

This is a fairly high efficiency, and this is due to the fact that the hammer is a simpler machine. The more complex a machine is, the greater are the losses in it due to friction, meaning there is a lower efficiency.