- #1
Tim Wellens
- 20
- 0
Homework Statement
The whole problem is in variables, which tends to confuse me a little.
We have two blocks that collide, Ma and Mb. Initially Ma experiences a positive velocity. Mb experiences a 0 velocity. Finally, Ma experiences a negative velocity, while we do not yet know Mb's final velocity. Mb=3Ma
Find which one of the blocks (if either) has a larger change in the magnitude of the momentum. Explain.
If the initial speed of block A is 20 m/s and the final speed is 5 m/s. What is the final velocity of block b?
In which case, if either, does block a exert a larger impulse on block b?
Homework Equations
p=mv
m1v1=m2v2
The Attempt at a Solution
1)[/B] I'm not sure how I would calculate variables with a change in magnitude any further than this
ΔPa= -MaVaf-MaVai= -2
ΔPb= MbVb-0=MbVb
So, block A has the larger change in the magnitude of the momentum since it would change by 2MaVa, while block B changes by 1MbVb.
2) Pai+Pbi=Paf+Pbf
Ma(20m/s) +0=Ma(-5m/s)+ 3MaVbf
divide Ma out of the left side, and the rest of the Ma's cancel.
20m/s= -5m/s+3Vbf
25m/s=3Vbf
Vbf=8.3m/s
3)I'm not sure how to calculate this. I know Impulse= J= Δp, and I know that block A overall exerts the greater magnitude of momentum. I guess for "which case" it must mean initial or final. I think in the final case block A would be exerting a greater impulse on block b because that's when block B actually has a velocity and moves from the impact of block a. But I am not sure how that relates to Δp, if we aren't dealing with both the initial and final, rather just one "case".