Question

5. In a workout, a weightlifter lifts a 75 kg weight 20 times. His arms raise the weight

.60 meters. How much work has he done?
Given, Unknown:
Equation, Substitute:
Solution:

Answer 1

The weightlifter has done a total work of 8,820 J

Explanation:

Mechanical Work

Is the amount of energy transferred by a force. It's a scalar quantity, with SI units of joules.

Being F the force vector and s the distance, the work is calculated as:

`W=F\cdot s`

Note this is the scalar version of the work which assumes both the force and displacement go in the same direction.

The weightlifter lifts a 75 Kg weight 20 times as part of his workout. The force he applies against the gravity is equal to the weight of the 75 Km mass.

F = W = m.g

F = 75 * 9.8 = 735 N

His arms raise the weight 0.60 meters, thus the work done on each repetition is:

W = 735 N * 0.60 m = 441 J

The total work for 20 repetitions is

20 * 441 J = 8,820 J

The weightlifter has done a total work of 8,820 J