Given parameters:
Mass of load = 20kg
Height of man = 1.4m
Unknown:
Work done by man = ?
Work done is the force applied to move a body in a particular direction.
Often times, it is mathematically expressed as;
Work done = Force x distance
In this problem, we use the formula of potential energy to find the work done;
Work done = Potential energy = mgh
where m is the mass of the load
g is the acceleration due to gravity = 9.8m/s²
h is the height of the body
Now, input the parameters, and solve for work done;
Work done = 20 x 9.8 x 1.4 = 274.4J
The work done by man is 274.4J