A balloon rises from rest with upward acceleration 1 m/s². At height 39.2 m a stone is released. Find the time for the stone to reach the ground (s), using g = 9.8 m/s² and the nearest integer.
Physics · Mixed Chapter
JEE Main Practice

Question

A balloon rises from rest with upward acceleration 1 m/s². At height 39.2 m a stone is released. Find the time for the stone to reach the ground (s), using g = 9.8 m/s² and the nearest integer.

G1 Physics · Accepted Answer

Step 1: Balloon speed at the release height is u = √(2ah) = √(2×1×39.2) ≈ 8.854 m/s upward. Step 2: The stone's height after release is y = 39.2 + 8.854t − 4.9t². Step 3: Setting y = 0 gives t = [8.854 + √(8.854² + 4×4.9×39.2)]/(9.8) ≈ 3.85 s. Step 4: To the nearest second, t = 4 s.