Question

A balloon has mass of 10 g in air The air escapes from the balloon at a uniform rate with velocity 4.5 cm/s If the balloon shrinks in 5 s completely Then, the average force acting on that balloon will be (in dyne)

• A. 3
• B. 9
• C. 12
• D. 18

Answer 1

Answer: (B)

9

Answer 2

dm = 10g
v = 4.5 cm/s
dt = 5s

$force = F = (\frac{dm }{ dt}) (v)$

i.e. $F = (\frac{10g}{ 5s}) × (4.5\frac{cm}s)$

$=9 {\frac{(gcm)} {(s)^2}}$

$= 9\, dyne$

Therefore, the correct answer is option (B): 9.