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A 0.4-kg model rocket is launched straight upwards. Its engine provides an impulse of 22 N*s by firing for 3 seconds. What is the average acceleration of the rocket while the engine is firing, and what is the maximum height the rocket will reach?

J=Ft so 22=F(3) so F=7.33

F=ma so 7.33=4a so a=1.83

x=(1/2)at(squared) so x=(1/2)1.83(3)squared so x=8.25 meters

then the engines cut off

the final velocity = at so v=(1.83)(3) so v=5.5 m/s

then using v(squared)=v0(squared) + 2a(x-x0) to find the displacement at the top of the arch I get 0 = 5.5(squared) + 2(-9.8)(x-8.25) so x = 9.79m

My two answers would be 1.83 m/s(squared) and 9.79 meters, correct or not?

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# Homework Help: Rocket firing problem

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