- #1
kipinator101
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Homework Statement
http://i.imgur.com/aeleeB9.png
Above is a diagram of a simple two-block mechanical system. Block A is initially sliding with some initial velocity and Block B is initially at rest. Block A and block B collide, stick together, and begin moving with some final velocity. Determine the final velocity of Block B.
Homework Equations
In this system, both energy and linear momentum are conserved quanties. It is easy for me to solve the problem using the conservation of linear momentum, but I am unable to solve the problem using conservation of energy. In this, I am asking help.
I asked my professor in class why you must use linear momentum to solve the problem. He said that internal energy was involved and that you must account for that. A question I want an answer to is, how do you determine the initial and final internal energies of the two block system? And are these the only two forms of energy that must be account for (KE and U, provided the blocks are in a vacuum and sliding across a frictionless surface)?
The Attempt at a Solution
Known Solution:
d/dt(Psys,x)=ƩFx + Ʃd/dt(min)*Vin - Ʃd/dt(mout)*Vout
→closed system, no external forces
∴ d/dt(Psys,x)=0
Integrate:
Pfinal -Pinitial = 0
Mblock,a*V0 = (Mblock,b+Mblock,a) * Vfinal
→Solve for Vfinal