# Question #799aa

##### 2 Answers

I found

But check my maths.

#### Explanation:

Ok, I considered that the absolute acceleration of the rockets is

Now I use

at this point the acceleration stops and the rockets reaches the maximum height (under influence of gravity

and

So:

I use this time

The maximum height of the rocket is **44.5 m**.

#### Explanation:

Here's how you can solve this problem without using the time of accelerated flight and the time of free fall.

You know that the rocket starts at ground level with an initial velocity equal to **zero**. After **20 m** of accelerated flight, the rocket reaches a height of **20 m**.

This means that you can determine the speed of the rocket when it shuts down its engines by

*After* it shuts down the engines, the rocket continues its upward flight under the influence of gravity, which means that the *gravitational acceleration*,

At *maximum height*, the speed of the rocket will be equal to **zero**. This means that you can write

Since you the expression for

Therefore,

The *maximum height* the rocket reached was