Q. From a balloon rising vertically upwards as $5\ {ms}^{- 1}$ a stone is thrown up at $10\ {ms}^{- 1}$ relative to the balloon. Its velocity with respect to ground after 2 s is $\left( assume\ g = 10\ {ms}^{- 2} \right)$
A) Zero
B) $5{ms}^{- 1}$
C) $10\ {ms}^{- 1}$
D) $20\ {ms}^{- 1}$
Explanation
(b) From equation of motion, we have
$v = u + gt$
Taking downward direction negative
$u = 10 + 5 = 15{ms}^{- 1},\ g = 10\ {ms}^{- 2},\ t - 2\ s$
$\therefore v = 15 - 2 \times 10 = - 2\ {ms}^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.