RELATIONSHIP FORCED VIBRATION AND NATURAL VIBRATION

Koshi high school Hiroya Ogawa 　

Satoki Yoshida

Motivation・Purpose

The earth quake of East Japan made Buildings broken. ↓ We decided to think the relationship between moving of object and forced vibration.

Important terms of our experiment

The vibration caused in an object by the power periodically received from an outside source.

The natural vibration caused, when the object freely move.

Important terms of our experiment

The phenomenon that sounds stress periodically change when two sounds having different frequency mix.

Important terms of our experiment

The phenomenon that the swing of the pendulum become larger when moving object received power matching natural peculiar frequency.

Object of this experiment

We applied forced vibration to the pendulum and checked the cycle and swing of beat.  　 　↓ We checked the relationship between them and the cycle of force vibration.

Tools used for our experiment・A vibration device made of  　LEGO MIND STORM

・A pendulum consisting of  　a light thread and suitable ball

Tools used for our experiment

・A sensor to measure the distance （PC software：Date studio）

・Stopwatch

Experimental method

Ⅰ

Experimental methodⅠ

Ｔ=2.48 Ｔhe cycle of the vibration device is 2.48s

Experimental method

Ⅱ Ⅲ

Experimental methodⅡ 　Ⅲ

1.53ｍ

Experimental method

Ⅳ

Experimental methodⅣ

Regular intervals

7.5mm

Experimental methodⅤ

Experimental methodⅤ

1.43ｍ 　

1.33ｍ 　

1.23ｍ 　

1.13ｍ

Experimental method

Ⅵ｜ｆ₁

－ｆ₂｜

When the pendulum is 1.53m 　

Max of swing 0.195 ｍ

When the pendulum is 1.43m 　Max of swing 0.134 ｍ The beat frequency Calculated 69.5 s Real 41 s

When the pendulum is 1.33m 　Max of swing 0.121 ｍ The beat frequency Calculated 33.6 s Real 38 s

When the pendulum is 1.23m

Max of swing 0.053 ｍ The beat frequency Calculated 21.3 s Real 21 s

When the pendulum is 1.13m

Max of swing 0.038 ｍ The beat frequency Calculated 15.0 s Real 16 s

The whole result of our experimentSwing was getting smaller. Beat frequency was getting bigger. Cycle of pendulum was getting smaller.

However… The length of pendulum which is near 1.53m, difference of the real score and calculated score was getting bigger.

↓  This reasons

The consideration of our experimentTo make pendulum do resonate,

We have to consider other powers from outside so as not to let them affect the experiment.

今後の課題

change

This experiment

Future research

Studying the way of making strong buildings

Or

Searching condition which can stand vibration