A balloon is moving vertically upward with a constant speed of 20 m/s. When it is at a height of 60 m above the ground, a small stone is released from it. Neglect air resistance and take g = 10 m/ $s^2.$ The time taken by the stone, after release, to reach the ground is:
Options

Question

A balloon is moving vertically upward with a constant speed of 20 m/s. When it is at a height of 60 m above the ground, a small stone is released from it. Neglect air resistance and take g = 10 m/ $s^2.$ The time taken by the stone, after release, to reach the ground is:

Options

G1 Physics · Accepted Answer

At release, the stone has the same upward velocity as the balloon, u = 20 m/s. Taking upward as positive and ground as y = 0: 0 = 60 + 20t - 5t^2. Thus t^2 - 4t - 12 = 0, giving t = 6 s (positive root). Hence option C is correct.

A balloon is moving vertically upward with a constant speed of 20 m/s. When it is at a height of 60 m above the ground, a small stone is released from it. Neglect air resistance and take g = 10 m/s^2. The time taken by the stone, after release, to reach the ground is: