Laws of Motion - Result Question 24

24. 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’?

[2014]

(a) 2mag+a

(b) 2maga

(c) mag+a

(d) maga

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Answer:

Correct Answer: 24. (a)

Solution:

  1. (a) Let upthrust of air be Fa then For downward motion of balloon,

Fa=mgmaFa=m(ga)

For upward motion,

(ii)Fa(mΔm)g=(mΔm)a

From equation (i) and (ii),

Therefore, Δm=2ma(g+a)



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