**Homework Notes**

**
HW 9**

*****
For *each part* of these problems, be very careful about what you choose as
the system and what you are using as initial and final states.

******
Just find equations that *could* be solved for the mass of the *X*^{+}
particle. Be sure that you have as many equations as unknowns. Use *θ* for
the angle that the pion is deflected and *
f*
for angle between the direction that the *X*^{+} particle goes and
the initial direction of the pion. When relating the energy of the particles to
their momentum, don’t assume that they are traveling slowly.

**“39”**
A 1-kg puck is sliding at 3 m/s and collides with a 2-kg puck which was
initially at rest. After the collision, the 1-kg puck is traveling at 2.24 m/s
at an angle of 63.4° from the direction it was originally going.

(a)
What is the velocity (magnitude and direction) of the larger puck after
the collision? (You may *not* assume that collision is elastic!)

(b) Was the collision elastic?

**Extra Credit**:
For two extra points each, find numerical answers to part (c) of 9.P.21 (the
height *h* of the block) and to 9.P.26 (the mass of the *X*^{+}
particle).