Posted by **eugene** on Tuesday, February 22, 2011 at 9:26am.

A 1-kg rocket is fired straight up from level ground. The engine is able to provide a constant 15N of thrust for exactly 5 seconds after which it shuts of completely. Find the maximum height that the rocket achieves.

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**bobpursley**, Tuesday, February 22, 2011 at 9:31am
WEll, the impulse given is 15*5 Ns=75Ns

Velocity at burnout= 75Ns/1= 75m/s

What was its altditude at this point?

Vf^2=Vi^2+2ad

where a= (F/m -g)

solve for d (height hi)

Now, final height

Vf^2=0=75^2-2g(hf-hi)

solve for hf.

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**Anonymous**, Tuesday, February 22, 2011 at 1:06pm
thanks so much...i got 33.3m/s...would u say that's correct?

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**charlie**, Tuesday, February 22, 2011 at 1:09pm
sorry that was 188 that i got

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