Question

the image shows a person in an elevator and also indicates direction of acceleration.

1. in which picture is the person’s weight decreasing?

a
b
c

Explanation:

To determine when a person's weight (apparent weight, the normal force \( T \)) decreases in an elevator, we use Newton's second law (\( F_{net}=ma \)). The forces on the person are gravity (\( mg \), downward) and the normal force (\( T \), upward). The net force is \( F_{net}=mg - T \) (if acceleration \( a \) is downward) or \( T - mg \) (if \( a \) is upward).

• For apparent weight \( T \) to decrease, \( T = mg - ma \) (so \( T < mg \)), which occurs when acceleration \( a \) is downward (since \( F_{net}=ma \) downward implies \( mg - T = ma \), rearranged to \( T = mg - ma \)).

Looking at the diagrams:

• In option A, if the acceleration direction (arrow \( a \)) is downward, the net force is downward, so \( T = mg - ma \), and \( T \) (apparent weight) decreases.

Answer:

A. (The option where acceleration is downward, leading to \( T < mg \) and decreased apparent weight)