Question

A ball is dropped from an elevator moving upward with acceleration ' $a$ ' by a boy standing in it. The acceleration of ball with respect to [Take upward direction positive]

• A. Boy is -g
• B. Boy is -(g +a)
• C. Ground is -g
• D. Both (2) & (3)

Answer 1

Answer: (D)

Upward direction $\to$ Positive
Negative direction $\to$ Negative
If a person is observing from ground then, for him the acceleration of ball is in the downward direction.
$a_{\text{ball }G}=a_{\text{ball }}-a_{\text{ground }}=-g-0$
$a_{bG}=-g$
$a_{bG}=$ Acceleration of ball w.r.t. ground.
$a_{\text{ball boy }}=a_{\text{ball }}-a_{\text{boy }}=-g-a$
$a_{bb}=-(g+a),a_{bb}=$ Acceleration of ball w.r.t. boy.