Question

A man in an elevator feels like he weighs 15 pounds less than his “normal” weight. Which of the following situations most likely explains this?
A) The elevator just started upward.
B) The elevator is coming to a stop on its way downward.
C) The elevator is coming to a stop on its way upward.
D) The elevator moved rapidly downward at a constant speed.
E) The elevator has been still for a very long time, and the man has indigestion.

Answer 1

The solution is easy as it is based in our day to day life event. We can simply answer it but in the language of physics, when the elevator is moving the body weight increases or decreases and it depends on the normal reaction whether it is the sum of mg and ma or subtraction of mg and ma where, m is the mass, a is the acceleration, and g is the gravity.

Complete step by step answer:
Step 1:
Weight of a body increases while going up and decreases as the body comes down. As we go up, the more downward force is exerted on our body. This can be explained by Newton's Third Law of Motion as, when we are moving up it means lift is exerting force on us from downward direction so that we move in upward direction.
Step 2:
Let us consider a diagram to answer the question in physics manner

In the above diagram we have assumed that a person is there in the elevator and it is moving downward.
The mass of the man is m and downward force will be mg
The normal reaction will be apposite to the mg
And acceleration will be downward.
So the actual weight of the body when in an elevator at rest will be mg.
When elevator starts moving with acceleration a then according to the Newton’s law of motion (third)
We get, ma = mg − N
Thus it seems that a part of the weight is spent on producing downward acceleration when a body is in the elevator.
So, N = mg − ma
Hence, the apparent weight of the body is less than the actual weight of the body.

Option C is correct.

Additional information: Newton’s third law: His third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal and opposite force on object A.

Note: The normal force is usually symbolized by N. In many cases the normal force is simply equal to the weight of an object, but that's only when the normal force is the only thing counteracting the weight. Hence weight is more than actual when moving upward and vice versa.