Can physics measure the work a porter does? What do you need to know to measure a porter's work? What produces work, and how is power different from work?

The body of a porter carrying load on head on a level road uses more energy than is required when the porter is resting completely. In this way the porter is doing some work.

However, when we think of theoretical definition of work, there is no force resisting the horizontal movement of the load when carried on a level road, and therefore there is no work done when a porter carrying a load on his head walk along a level road.

When the porter is going down the stairs the gravitational energy acting on the load is assisting the downward movement of the load. In this way energy is released by downward movement of the load. Thus the porter is doing negative work on the load.

50 inches should be the resultant vector

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.