Answer:
To calculate the work done by the man, we need to determine the force he exerted and the distance over which he exerted that force.
In this case, the man is carrying the child on his shoulder while standing on a spot, implying he is not moving vertically. As a result, the vertical force (upward or downward) cancels out, and no net work is done in the vertical direction.
However, the man is supporting the weight of the child, which creates a force against gravity acting vertically downwards. This force is equal to the weight of the child given by:
Weight = mass × gravitational acceleration
For the child, let's assume a mass of 20 kg.
Weight of the child = 20 kg × 9.8 m/s² (approximate gravitational acceleration on Earth) = 196 N
Since the man is carrying the child for 2 hours, we need to convert the time from hours to seconds:
Time = 2 hours × 60 minutes/hour × 60 seconds/minute = 7200 seconds
Now, we can calculate the work done by the man using the formula:
Work = Force × Displacement × cos(angle)
As the man is standing in one spot, the displacement is zero, and the angle between the force exerted and displacement is 0 degrees. Thus, cos(0) = 1.
Work = Force × Displacement × 1 = Force × Displacement
Therefore, the work done by the man is:
Work = 196 N × 0 m
Work = 0 Joules (J)
Since the displacement is zero, the man does not perform any mechanical work in this scenario.
It's important to note that while the man spends energy and effort carrying the child, from a physics perspective, no net work is performed as there is no displacement along the direction of the force exerted.