JAMB Physics 2015 Paper

Concept:Efficiency measures how much useful work a simple machine delivers compared to the work put into it.It links mechanical advantage and velocity ratio mathematically.Explanation:Mechanical advantage $(M.A)$ is the factor by which a machine multiplies the input force.Velocity ratio $(V.R)$ is the ratio of the distance moved by the effort to the distance moved by the load.Efficiency $(e)$ is the ratio of useful work output to total work input, expressed as a percentage.For an ideal machine with no friction, $e = 100\%$, but in real machines $e < 100\%$.The standard relation is:$$e = \frac{M.A}{V.R} \times 100\%$$This means efficiency equals the fraction of the velocity ratio that is realised as mechanical advantage, multiplied by $100$.Answer:Option A: $e = \frac{M.A}{V.R} \times 100\%$.