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Thinh Nghiem
Thinh Nghiem • Mar 17, 2019

Can a gyroscope change its rotating direction?

In school, I had chance to learn about the movement of the gyroscope, its orbits, dynamic energy etc.

However the spinning direction  was not referred to.

Recently I played with a spindle, a China made toy. With my surprise, during its movement, the spindle changed its direction from anti clockwise  to clockwise and vice versa. I am not sure my observation is correct since it spins so fast.

I recorded  this movement into a clip and posted it in Youtube with link

Please watch it and give me comment if I am right or not. Decreasing the speed of the clip in Youtube can be helpful for exact observation.

To say in brief, my question is, can a gyroscope change its rotating direction during movement? In my thinking, it’s very hard to surpass inertia when rotating is in progress

All feedback are welcomed

No. A free spinning Gyro cannot change its direction of rotation on its own during a run. One can start a gyro in either direction. One has to wait till it stops before making it go the other way.

From the reflection on the table top it appears that there is a fluorescent tube light above. If it is running on an AC power supply, what you see can be explained by stroboscopic effect. I have seen similar anomalous behaviour even with a spinning coin under suck a light.

Please check out this video. The blades of the helicopter appear to spin both ways.

Anoop Kumar
Anoop Kumar • Mar 18, 2019

It didn't change the direction. Initial the rotation speed was matching such a way they it seems anti-clockwise but when speed goes down the speed and shutter speed of camera matched such that it seems clockwise. 

Do you think the the rotation speed of florescent strip on top is same as actual speed of gyroscope? No. It just matching the speed of shutter speed. 

See below. Similar effect happened for our eyes too.

Ramesh RR
Ramesh RR • Mar 18, 2019

Have you seen the ads on TV about some car or other? Most of the time, the wheels seep to be rotating the wrong way !!!   Stroboscope effect. There have been cases where people have walked into spinning propellers thinking they are stationary.

@Anoop Kumar , while you are right the thing happened when he was seeing with his eyes. That can happen at speeds which are near multiples of the strobe frequency or specific fractions. It is easy to calculate. It is similar to stop motion animation. If the frequency of the light is slightly above the speed of the spinner, every subsequent image will be slightly ahead leading to a forward motion or clockwise for rotation. The reverse happens when the strobe speed is slightly less.

The tube light flickers at double the frequency of the AC supply. The spinner is gradually slowing down. At some speed the direction appears to change.

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