# Rocket ship

1. Feb 24, 2005

### jenduncan

A rocket is launched straight up with constant acceleration. 4 seconds after liftoff, a bolt falls off the side of the rocket. The bolt hits the ground 6.10s later. What was the rocket's acceleration?

rocket: xfinal = 1/2a^2 x 4s^2
bolt: vfinal = 0+ -9.9 m/s^2 * 2.1s
given this vfinal, of -20.58 m/s, then x = 21.61 for distance traveled

using 21.61 for the rocket, 21.61=1/2a(4s)^2
a = 2.7m/s^2
This isn't the correct answer. Could you please show me how to set this problem up? HELP.
Thanks.

2. Feb 24, 2005

### vincentchan

what is the initial velocity of the bolt? (same as the rocket velocity @ t=4) write down one equation for this

what is its initial height? (same as the rocket height @ t=4) write down another one

the bolt hit the ground at 6.10 sec later, you can write one more equation for this...

now you have 3 equation and 3 unknown (initial height, initial velocity, rocket accelation)