Q. A balloon with mass 'm' is descending down with an acceleration 'a' (where a < g). How much mass should be removed from it so that it starts moving up with an acceleration 'a' ?
A) $\frac{2ma}{g + a}$
B) $\frac{2ma}{g - a}$
C) $\frac{ma}{g + a}$
D) $\frac{ma}{g - a}$
Explanation
[Solution] Buoyant force B: mg − B = ma and B − (m − Δm)g = (m − Δm)a. Adding gives $\Delta m = \frac{2ma}{g + a}$. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.