Suppose a man lifts 20 boxes each of mass 15kg to a height of 15m. Determine the work done by the man against gravity?

The work done by the man against gravity can be calculated using the formula:

Work = Force x Distance

In this case, the force is equal to the weight of the boxes being lifted, which is equal to the mass of each box multiplied by the acceleration due to gravity (9.8 m/s^2). So, the force is:

Force = 15kg x 9.8 m/s^2 = 147 N

The distance over which the force is applied is the height to which the boxes are lifted, which is 15m.

Therefore, the work done by the man against gravity for lifting one box is:

Work = Force x Distance = 147 N x 15m = 2205 J

Since the man lifts 20 boxes, the total work done by the man against gravity is:

Total work = 2205 J x 20 = 44100 J

Therefore, the work done by the man against gravity for lifting 20 boxes each of mass 15kg to a height of 15m is 44100 Joules.

Given:

- Mass of each box: 15 kg
- Number of boxes: 20
- Height lifted: 15 m

Concept:

Work done against gravity is equal to the product of force and displacement in the direction of the force.

Calculation:

Firstly, we will find the total mass lifted:

Mass lifted = Mass of one box × Number of boxes
Mass lifted = 15 kg × 20
Mass lifted = 300 kg

Next, we need to calculate the gravitational force acting on the total mass:

Gravitational force (F) = Mass (m) × Acceleration due to gravity (g)
F = 300 kg × 9.8 m/s²
F = 2940 N

Finally, we can calculate the work done against gravity:

Work done (W) = Force (F) × Displacement (d)
W = 2940 N × 15 m
W = 44100 J

Therefore, the work done by the man against gravity is 44100 J.