# Homework Help: Rocket Project - need to find mass of rocket to reach 15 m altitude

1. Mar 15, 2013

### ganoobinator

Rocket Project -- need to find mass of rocket to reach 15 m altitude

I have a project for grade 11 physics, i have to create a rocket that reaches precisely 15 m altitude, and all Im given is the thrust profile of the engine (force(N) vs time(s) graph)

It is an Estes A8-5 engine

i have used calculus to integrate and find the impulse, which is 2.50N*s, total burn time is 0.7s

im stuck, i cant find the mass without the acceleration, i cant find the acceleration without the final velocity after burn.

ive tried everything i can think of, even energy problems, cant seem to figure it out.

2. Mar 15, 2013

### rude man

What exactly are you supposed to come up with? Mass of rocket?

Final velocity is zero, right, if it's supposed to go just 15m? And is that miles or meters?

3. Mar 15, 2013

### haruspex

A critical question is whether you need to take into account the reduction in fuel mass during ascent. If so, you need to develop and solve the differential equation for a rocket. Otherwise, energy should be the way. you know the total energy the rocket delivers, and you know the height to be reached.