kinematics question 5

Question

A balloon is moving upwards with velocity 10 ms^-1. It releases a stone which comes down to the ground in 11 s. The height of the balloon from the ground at the moment when the stone was dropped is :
(A) 495 m (B) 592 m (C) 460 m (D) 500 m

Answer 1

A balloon moving upwards with constant velocity 10m/s . if we release the stone from balloon , then, initial speed of stone = 10m/sec .

now, 
initial speed = 10m/sec 
time = 11sec 
let H is the height of balloon when stone is dropped .

use kinematics equation , 
S = Ut + 1/2at² 
-H = 10 × 11 - 1/2 × 10 × (11)² 
= 110 - 5× 121 
= 110 - 605 
= -495 m 
- H = -495 m

hence, H = 495 m 

so, height of balloon is 495m when stone is dropped .