Comments for Tutorial Homework 6

Things you need to know before solving these problems are how to obtain the resultant pulse when two pulses interfere and how to handle the reflection. Problems 1., 2., and 3. can be solved by this knowledge. Problem 3. guides you through the process of obtaining the boundary condition for the free end reflection. You need to incorporate what you have already learned before and what you have newly learned.

3.a. If you already know the result, the argument may seem to be repetitious. (Yeah, I agree.) I emphasized the logic: how to reach the conclusion. If you look at the key carefully, you should be able to follow how the argument goes on.

3.d. & e. If you are not aware by now, the boundary condition for the free end reflection is that the spring be perpendicular to the rod very near the rod. e.ii. seems to violate this.

4. You can immediately know that some of the frames are clearly wrong by considering the boundary conditions (1, 2, and 5 in the key). To identify all the errors, you need to actually construct the resultant pulse, as you did in 2. and 3.d. & e. For 4 and 6 in the key, I didn't assume the boundary condition was violated, because if you look very closely near the boundary, the spring may still be flat (horizontal) in that very small region.