Physics Question About Work Being Done

Question

What work do you think is done when you carry a 20 N weight backpack for a 1000 m walk? will the work be positive, negative, or potentially zero?

Answer 1

The answer depends on the angle of the incline and your physiology.

Let

w = 20 N be the weight,

s = 1000 m be the distance,

α be the angle between the path and the horizontal.

The resulting change in the potential energy of the weight will be

sin(α)ws

That also equals the work needed in the transfer of the weight.

It will be 0 for level ground, positive for an uphill walk and negative for a downhill walk.

However, we also need to take into account your physiology.

First we need to add your weight to the weight w.

Secondly, when we walk we raise our body a few centimeters with every step,

which involves positive work.

Thirdly, there are other bodily functions, like breathing, which increase during you walk.

Those also require energy, i.e., work.

The upshot is that the work may be positive, negative or zero.

Work of zero happens in case of a slight downhill walk.