Question

56. A rocket is fired vertically from the ground. It moves
upwards with a constant acceleration of 10 m/s?
After 30 seconds the fuel is finished. After what
time from the instant of firing the rocket will it attain
the maximum height ? g = 10 m/s?:​

Answer 1

Answer: 60 sec.

Explanation:

When fuel is finished, the acceleration of rocket will become zero. The rocket will move with initial velocity and contant acceleration g.

Calculate velocity after 30 second of firing. V= u +at

V= 0 +10x30

V= 300 m/s

When fuel has finished the rocket will achieve this velocity.

Now rocket will move upward with velocity 300 m/s and retardation g due to gravity.

It will reach maximum hight when it's velocity becomes zero.

Use v=u-gt

0= 300 - 10*t

300= 10xt

t= 30 sec.

Total time from launching is 30 +30 = 60 sec