(adsbygoogle = window.adsbygoogle || []).push({}); 1. Problem

A launched rocket emitting gas with a speed of 1500 m/sec relative to rocket and with flowrate of 100 kg/sec.

If net mass of rocket is 5000 kg, find it's acceleration.

2. Equations

F=ma

F=d(mv)/dt

Conservation of momentum

m_{1}u_{1}+ m_{2}u_{2}= m_{1}v_{1}+ m_{2}v_{2}

3.Attempt

Flowrate = 100 kg/s

velocity = 1500 m/s

momentum downwards = mv = 100 x 1500 = 1.5 x 105 kg m/s

According to conservation of momentum, i found the velocity to upward direction.

m_{1}u_{1}+ m_{2}u_{2}= m_{1}v_{1}+ m_{2}v_{2}

0 = -100 x 1500 + 5000v_{2}

5v_{2}= 150

v_{2}= 30 m/s

what should do next to find the acceleration

If I use F=d(mv)/dt

what is the initial velocity and final velocity. I have no idea about those two & and how to take it.

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# Homework Help: Acceleration of the rocket

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