Science Buddies: "Ask an Expert"

My son and I have built the seismograph described in the "whole lot of shaking going on" project. The arm moves freely, and when I set the seismograph on a table to shake it, it seems to work slightly. However, when we set it on the ground or the driveway, or the hallway floor, it does not do anything when we drop weights or jump up and down in order to cause vibrations. Has anybody had any success with this project? My son's science fair at school is in a couple of weeks, so it is too late to start over with something else. Any help would be greatly appreciated.

Hello,

That is great you helped your child build and test the seismograph. I haven't done this project myself, but I can help you troubleshoot a bit. Are you sure the recording arm can move freely? If you attached a weight to keep it from moving with very slight vibrations, can you check it to see if the weight is too heavy?

I will ask the other experts for some additional help.

Tonya

The arm moves freely, my son or I can push it one way and it will sway back and forth ( with or without the weight on the beam). The weight itself is 230 grams. When the seismograph is sitting on the ground, it does not work, regardless of whether the weight is on the beam or not. For the base, we used a 12 inch by 24 inch piece of poplar board that is half an inch thick. I was wondering if maybe this was too thick, and was perhaps insulating the seismograph from any vibrations.

It sounds like you made the base using the wood of the same thickness in the method we described. You can test that - by placing the seismograph on the table and giving it a good shake at the table legs. You should be able to record a good line movement... which it sounds like you did not get yet. Have someone watch the beam when you shake the table - perhaps it is moving well, but you aren't getting a line on the paper...

Perhaps the weight is not heavy enough? Your weight is 230g. We suggested a brick, which is about 2300g. Can you find something heavier to place on the beam? It might not be weighted down enough to keep the pen on the paper for the recording.

Or maybe the pen isn't good enough to make a mark. A marker might be better.