Laws of Motion

JEE Main level, single correct, medium

23 of 210

Question 23 of 210

A balloon has mass of 10g10g in air. The air escapes from the balloon at a uniform rate with velocity 4.5cms−14.5cm{s}^{-1}. If the balloon shrinks in 5s5s completely. Then, the average force acting on that balloon will be (in dyne).

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Answer: (B) 99

Given that the mass of the air m=10gm=10g and it escapes in time t=5st=5s with velocity v=4.5cms−1v=4.5cm{s}^{-1}.
The average force on the balloon can be given as,
F=vdmdtF=v\dfrac{dm}{dt}
⇒F=4.5×105=9dyne\Rightarrow F=4.5\times \dfrac{10}{5}=9dyne

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