# Question #754ff

##### 2 Answers

**Answer**

Given

Velocity gained in 30s is

1.**The engine fails** at this moment and rocket undergoes free fall under gravity.If it reaches height **h** at this point then

After 30s of its journey it will go up with retardation

2.At this highest point it will have a downward acceleration

If it ascends a height

If the rocket takes Ts to fall back at launch pad **after its engine fails** then

Displacement during Ts is

Initial velocity upward

And

So

So the total time to return back at the launch pad after it was launched will be

3.

1.

Given Initial velocity of rocket

Upwards Acceleration of the rocket

Duration of upward acceleration

Velocity **assuming upwards direction is positive**.

After engine fails the rocket undergoes free fall under gravity with initial velocity calculated above. Let it reach height

2. Thereafter, first it goes up and is retarded under gravity

3. Suppose the rocket takes

Displacement during time

Setting up the kinematic equation we have

Using the quadratic formula

Ignoring the