Posted by **Adrienne** on Tuesday, November 3, 2009 at 10:08pm.

A speed velocity of a a rocket with a mass of 0.25 kg passes from 15 m/s[up] to 40 m/s[up] in 0.60s. calculate the force of the escaped gasses of the rocket.

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that's what i've done, so far

data: m = 0.25kg

initial velocity = 15 m/s

final velocity = 40 m/s

time = 0.60s

final velocity - initial velocity / time = acceleration

40 m/s - 15 m/s / 0.60 s = 41.67 m/s^2

for here the solutions for the problem says that the next formula that needs to be used is FORCE = MASS (GRAVITY + ACCELERATION) why is that.

and why would you not use the formula

force = mass x acceleration ?

- physics 20 -
**Jordan**, Wednesday, November 4, 2009 at 7:58am
acceleration due to gravity must be factored in as the rocket is traveling upwards. since you have chosen up to be positive acceleration down must be negative, making gravity -9.8m/s

the equation is still

force=mass x acceleration

accept the formula used to calculate acceleration does not factor in gravity, the value calculated will just assume that no other forces are acting on the rocket

i know this may not be the best clarification so ask away with any problems :)

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