A block-and-tackle system is used to lift a load of 20N through a vertical height…

A block-and-tackle system is used to lift a load of 20N through a vertical height of 10m. if the efficiency of the system is 40%, how much work is done against friction?

Correct Answer: Option C

Explanation

Efficiency = (frac{output}{input}) x 100
40 = (frac{20times10}{input}) x (frac{100}{1})
input = 500J
work against friction = input – output
= 500 – 200 = 300J