Question

A rocket is launched to travel
vertically upwards with a constant
velocity of 20m/s. after travelling for
35s the rocket develops a snag and
its fuel supply is cut off. The rocket
then travels like a free body. What is
the total height achieved by it?
After what time of its launch does it
come back to earth?

Answer 1

The rocket is at a height of 700 metres after the launch.

Answer 2

S = ut

This is because it is moving at a constant velocity.

After 35 seconds the distance will be :

S = 20 × 35 = 700m

Now from 700 m above the ground now it travels at a free fall.

The initial velocity = 20 m/s

Final velocity = 0

Acceleration due to gravity = 10

Now :

V² = U² - 2gs

0 = 400 - 20S

20s = 400

S = 400/20

S = 20 m

The total height achieved = 700 + 20

= 720 m

Time it takes to drop back to the earth is :

S = ut +  0.5gt²

u = 0

720 = 0.5 × 10 × t²

720 = 5t²

t² = 720/5

t² = 144

t = √144

= 12 seconds

The total time it takes is :

12 + 35 = 47 seconds