Sandra used a ramp to slide a chair onto the back to a truck. She used 10 N of force and the ramp was 4 m long. The chair itself had a mass of 3.6 kg. The distance from the back of the truck straight down to the ground was 1 m. Calculate the efficiency. (Note: 1 kg = 10 N).
using the note
the energy gained by the chair is ... 3.6 kg * 10 N/kg * 1 m = 36 Joules
the work done by Sandra is ... 10 N * 4 m = 40 Joules
the efficiency is ... (36 J / 40 J) * 100%