# Carrying a Gyroscope Upstairs

#### areid10990

1. I am carrying a briefcase in which sits a gyroscope whose large angular velocity points forward horizontally. When I try to climb stairs, what happens to the briefcase?

2. 0=$$\Delta$$$$\vec{}L$$

3. My intuition says that the briefcase would point downward, but I really don't know how to approach this problem. It doesn't seem to me that climbing up stairs would alter the angular momentum in the system.

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#### Delphi51

Homework Helper
I think your intuition is correct! It is like carrying a gyrocompass in an airplane. As the plane goes up, the gyrocompass doesn't change the plane's orientation.

If you turn the briefcase, the wheel of the gyroscope will not turn with it. The angular velocity will remain pointing forward, but no torque will oppose the turning of the briefcase because "gyroscope" means the wheel is mounted on gimbals and the case is free to turn relative to the wheel.

If you try to turn a flywheel not mounted on gimbals, you will experience that counter intuitive torque in an unexpected direction. Try it with an angle grinder at high speed.
See http://en.wikipedia.org/wiki/Gyroscope

#### areid10990

Thanks for your reply. It seems reasonable to me that there is no real force feedback between the gyroscope and the briefcase, so nothing would happen, but the way the question is phrased in the book suggests that something does happen. The question before it asks what would happen if you tried to turn left with the briefcase

#### Delphi51

Homework Helper
I would head straight for the lab and ask to play with a gyroscope.
Hopefully they have a nice battery powered one - the string-pull ones are a pain, but you can find them for a reasonable price at a toy store.

#### areid10990

Haha yeah, I was looking around for something to simulate it but alas I have no such resource at my disposal before this is due. Thanks for your help, I'm sure it will come to me soon

#### areid10990

Ended up figuring it out. Nothing happens. I realized that walking up the stairs puts one (approximately) in an inertial reference frame. Surely the stairs moving behind me could not affect the motion of my briefcase.

"Carrying a Gyroscope Upstairs"

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