JEE Main · 2021 · 25 Jul 2021 · Shift 2 · Kinematics

A balloon was moving upwards with a uniform velocity of

10 m/s

. An object of finite mass is dropped from the balloon when it was at a height of 75 m from the ground level. The height of the balloon from the ground when object strikes the ground was around :
(takes the value of

g

10 m/s^{2}

)

(A)250 m
(B)300 m
(C)200 m
(D)125 m✓ Correct

Answer: (D)

Solution

The object leaves the balloon carrying the balloon's velocity,

10

m/s upward, from a height of

75

m. Taking upward as positive and the ground as the origin,

0 = 75 + 10 t - 5 t^{2}

t^{2} - 2 t - 15 = 0

and

t = 5

s. Through these

5

s the balloon keeps rising at a uniform

10

m/s and climbs a further

10 \times 5 = 50

m. Its height above the ground when the object strikes is

75 + 50 = 125

JEE Main · 2021 · 25 Jul 2021 · Shift 2 · Single correct option

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