The answer is 62.5N; Efficiency of the wheel and axle system(e)=80%
Velocity ratio of the system(V.R) = 4
Mechanical Advantage of the system(M.A) = ?
e = M.A/V.R ✖ 100
80% = M.A/4 ✖ 100
Make "M.A" the subject of the formula
M.A = 80/100 ✖ 4
M.A= 3.2
Load on the wheel and axle system (L) =20kg = 200N
Efforts required to lift the Load (E) = ?
M.A = Load/Effort
3.2 = 200/ Effort
Make Effort the subject of the formula
Effort = 200/3.2 = 62.5N
Therefore the Effort to lift a mass of 20kg is 62.5N
