Two blocks, of masses M and 2M, are placed next to each other on a horizontal smooth surface. The blocks are connected by a light spring with force constant k.

Initially, the blocks are at rest. Then block M is given a quick push directly away from block 2M so that it acquires velocity v. Find the displacement of block M by the next moment its velocity equals v again.

We received a large number of solutions to our October Challenge, Up and away…. The solutions came from all over the world. Many of the solutions, alas, were incorrect.

We are pleased to recognize the following successful solvers:

Guidelines for contributors

Many thanks to all contributors and we hope to hear from many more of you in the future!

Note: as always, we would very much appreciate reader-contributed original Challenges.

Boris Korsunsky, Column...

AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.