Problem 8-61 Cons. of Momentum - Part 8

A space vehicle and its fuel tank are moving with a velocity of \(350\; m/s\) toward a space station. The fuel tank is then jettisoned to the rear so that its velocity is only \(250\; m/s\) toward the station. What is the new speed of the space vehicle? The mass of the vehicle is \(3.25\) times that of the tank. [Ans. \(380\; m/s\)]


Accumulated Solution

Diagram A

Solution Before After
(B) \((m_1 + m_2)v\) \(m_1\; v_{1}{'} + m_2\; v_{2}{ }'\)

Correct!

The explosion (or whatever is used) to separate \(m_1\) and \(m_2\) exerts only internal forces on the system.

Therefore momentum is conserved.
\((m_1 + m_2)v = m_1v_1{'}  + m_2\; v_2{'}\)
 
\((m_1 + 3.25\; m_1)(350) = 250\; m_1 + 3.25\; m_1v_2 {'} \\ (4.25)(350) = 250 + 3.25\; v_2{ '} \\ v_2{ '} = [(4.35)(250) – 250]/3.25 = 380 \;m/s\)

 

You have completed this problem. 

 

Please see Alternative solution.