Please solve question number 17 and 18

17. A balloon which is ascending at the rate of 12 m/s is 30.4 metre above the ground, when a stone is dropped. After what time the stone will reach the ground? [Take g = 9.8 m/s²]
(1) 3 s
(2) 3.5 s
(3) 4 s
(4) 6 s

 

Dear Student,

Ans17.
When the stone is dropped:

Its initial velocity, u = 12 m/s (upward)

Acceleration, a = -9.8 m/s² (downward)

Displacement, S = -30.4 m (downward)

Time taken to reach ground, t

Using,

S = ut + ½ at²

=> -30.4 = 12t – 0.5×9.8×t²

=> t = 4 s

Ans4. 4 seconds

P.S. Kindly post separate questions in separate threads.

Regards