A model rocket is propelled upward by a cylinder of compressed water. The cylind

Question

A model rocket is propelled upward by a cylinder of compressed water. The cylinder emits water at a rate of 0.050 kg/second with an exit speed of 80.0 m/s. Initially, the rocket has a mass of 0.15 kg, including the water cylinder. What is the rocket's initial upward acceleration? Don't forget to add in the downward force of gravity. Hint: what is p of the water in t = 1 second?
a)17 m/s2.
b)9.8 m/s2.
c)36 m/s2.
d)27 m/s2.
Force expressed in terms of momentum is
a) F = p / x
b)F = p / t
c)F = p / t
d)F = p x v

Explanation / Answer

Using Momentum Conservation -
Initial Momentum = Final Momentum
Mass of water * Velocity of water = Mass of rocket * initial velocity of rocket
0.050 * 80 = 0.15 * v
v =  (0.050 * 80)/0.15 m/s
v = 26.66 m/s

Initial Velocity = 0
Final Velocity = 26.66 m/s
Time = 1s

V = u + a*t
26.66 = 0 + a *1
a = 26.66 m/s
Downward Acceleration = 9.8 m/s^2
Initial upward acceleration = 26.66 + 9.8 = 36.4 m/s^2

Option c is correct , a = 36 m/s^2

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