- #1

- 103

- 0

## Homework Statement

Attached in the files, scan from Resnick and Halliday. Also the answers (notice that I use a different meaning for [tex]u[/tex], but it shouldn't matter.

## Homework Equations

Conservation of momentum, and conservation of energy.

## The Attempt at a Solution

Initial Energy of the system is [tex]mgh[/tex], initial momentum is 0.

I'll call the velocity of the wedge [tex]u[/tex] and the velocity of the block [tex]v[/tex].

The equations:

[tex]2mgh = mv^2 + Mu^2[/tex] - all potential energy goes to the velocities of both objects.

[tex]Mu = -mv \cos \alpha[/tex] - conservation of momentum - only the horizontal component of [tex]v[/tex] is taken into consideration.

I end up having this as an answer:

[tex]u = \sqrt{\frac{2gh}{M^2 + Mm \cos ^2 \alpha}}m \cos \alpha[/tex]

Which is, not correct according to the answer.

What did I do wrong?

#### Attachments

Last edited: