Momentum conservation when clay block collides with cart

[ryankunzzz]

Homework Statement

Homework Equations

Conservation of liner and angular momentum
H1=H2
r x M₁V₁= r x M₂V₂

G1=G2
M₁V₁=M₂V₂

The Attempt at a Solution

I've gotten an equation for the velocity of the block and clay after the impact, and I also know that when the block reaches the highest point of its arc, its linear velocity is going to be the same as the velocity of the cart. Is the momentum going to be conserved and I can say M_bV₁=V_tot(M₁+M₂+M₃)

 

[TomHart]

Is the momentum going to be conserved and I can say MbV1=Vtot(M1+M2+M3)

It seems like that would be true. On the other hand, I'm thinking, "It seems too easy. Am I missing something?" But I can't think of what that might be.

 

[haruspex]

Is the momentum going to be conserved and I can say MbV1=Vtot(M1+M2+M3)

Yes, and I believe that is where the hint is directed.

 

[ryankunzzz]

But what about the about the change in potential energy as the arm swings upward?

 

[haruspex]

But what about the about the change in potential energy as the arm swings upward?

What about it? That's energy, not momentum.