The efficiency of a ramp is computed using the notion of mecanical work. It is force multiplied by the displacement, if force and displacement has the same directions.
`W = F*d.`
Our goal is to lift a box on a height, in this case a 600N box 2m high. The work needed for direct lifting is
When we use ramp, the force lowers, 300N, but path become longer, 5m. The product is
So we make 1500J of work instead of theoretically possible 1200J. The efficiency is
`1200/1500=0.8,` or 80%. This is the answer.
(we use ramp because while losing in work, we can exert lower force. The entire weight may be too great for us)