How to make a 10 second timekeeper?

Question

My 6th grader has a project that I am stumped on. It has to be a timer that measures 10 seconds consistently, opperate with little effort, and sturdy. It will be measured on square centimeters, cubic centimeters, and mass they are looking for it to be small and light weight and has to be aesthetically pleasing. Wow they are not asking for much are they and this is only 6ht grade! Thank you for anyone who can help me with any ideas.

Answer 1

I'm not sure this belongs in the math section; it's more like an engineering or physics problem.

My first ideas include:

1. A water source with a hole in it. Release the cover on the hole and when the water runs out you're done. Problem -- if it's from a hard substance it could be hard to make, while if it's from a soft one the hole could widen with repeated use, detracting from accuracy.

2. Alternatively, water runs through a known hole into a receptacle, and when the receptacle overflows, you're done. The advantage of the latter is that if the receptacle is a little to big, you can calibrate by dumping some objects in to reduce the effective volume.

3. A marble rolling down an inclined plane. Change the angle of the plane until you get 10 seconds. This one will be pretty big, however, whereas the water one could be small if the hole is small.

4. A very small pendulum. 10 seconds would be a lot of swings on the pendulum, so as to keep the whole thing small. You need a lot of weight in the base for stability, relative to the overall size of the thing, but so be it. Having it swing by a lot less than a full 180 degrees might be a good choice to help with stability.