# Homework Help: 2 moving masses

1. Nov 28, 2007

### ahello888a

1. The problem statement, all variables and given/known data - In this problem, "m" slides down "M" (that is inclined at angle alpha) to the point "P" at the bottom-right of the triangle. "m" starts with zero velocity and "M" starts with zero velocity. There is zero friction between "m" and "M". There is also zero friction between "M" and the surface that it rests on (not shown in picture). So the questio is what is the velocity of "m" when it reaches the "P"? I don't even know how to approach this problem, so I dont have any work done, but my teacher told me that I would have to use the conservation of linear momentum and mechanical energy. Thanks for all the help.

2. Relevant equations - Emech = delta k + delta u; p = m1v1f + m2v2f = 0

3. The attempt at a solution - my teacher mentioned the relavent equations. but i really dont know how to even start this problem. i only know that for the free body diagram of "m" that theres sumFy = n-mgcosalpha; mgsinalpha to the right and for "M" umFy = n-mg; i know for sure that the free body for "M" is missing forces from the "m" but im not sure how to account for that

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2. Nov 29, 2007

### Bill Foster

$$m$$ is a block and $$M$$ is a wedge?

3. Nov 29, 2007

### ahello888a

yes that is correct

4. Nov 29, 2007

### Bill Foster

Is the point "P" on the wedge or on the flat surface?

5. Nov 29, 2007

### ahello888a

it is on the wedge

6. Nov 29, 2007

### Bill Foster

Never mind. I can see your attached image now.

7. Nov 29, 2007

### ahello888a

haha. im so sorry i didnt mention that.

8. Nov 30, 2007

### rl.bhat

What is the direction of the velocity of M?

9. Dec 3, 2007

### ahello888a

The direction will be to the left, but it has no initial velocity. Nothing in this system has an initial velocity. "m" is released from rest and will slide down by gravity and since the surfaces are frictionless, "M" will begin to move as a result of gravity pushing down on "m" pushing down on "M"