Question 54

A rocket is launched to travel vertically upward with a constant velocity of 20 m/s. After travelling for 35 seconds, the rocket develops a snag and its fuel supply is cut off. The rocket then travels like a free body. The height achieved by it is:

Solution

we know that

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

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