Car gyroscopic effect problem/doubt

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Discussion Overview

The discussion revolves around the gyroscopic effects experienced by a car with a rotating flywheel when subjected to external torques, both in free space and on a road. Participants explore the implications of these effects on the car's ability to steer and the perceived resistance during turns.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that in free space, the car will precess rather than steer when jets are fired, as the torque from the jets is perpendicular to the angular momentum vector of the flywheel.
  • Others argue that if the car is on the road and heavy enough to maintain contact, it will not experience resistance when steering, assuming the flywheel is prevented from precessing.
  • A participant questions whether the car would still feel "heavier" during a turn if it has a stiff suspension and does not allow for precession, suggesting that angular momentum conservation might not allow for precession in this scenario.
  • Another participant asserts that the car will still seem "heavier" during a turn, regardless of the suspension characteristics.

Areas of Agreement / Disagreement

Participants generally agree that the car will precess in free space and that it will feel "heavier" during a turn. However, there is disagreement regarding the effects of suspension and the conditions under which resistance to steering may be felt.

Contextual Notes

There are unresolved assumptions regarding the behavior of the car's suspension and the nature of the materials involved, as well as the specific conditions under which the flywheel's precession is restricted.

Shivanand
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Problem Statement

Suppose a car has mass M. It has a flywheel with axis running from front to back between left and right set of wheels. Let the flywheel have moment of inertia I and let it rotate clockwise at a constant angular velocity of w (omega). The flywheel shaft is held inside two bearings (front and back and it turns clockwise as seen from back of the car. Assume the shaft is massless (See the attached image).

1) If the car is not on road and in free space (vaccuum), if jets are fired from left-front and right-rear corner so that there is a torque tending to steer the car right, can the car steer or does it precess in vertical plane? If it steers, what is the minimum angular velocity of the flywheel to prevent the steering motion?

2)If the car is on road and it is heavy enough to stay in contact with road at all times, and it tries to take a right turn (steer right). The bearings are strong enough to prevent the flywheel from precessing in vertical plane. So the flywheel essentially is not allowed to precess. Will there be any resistance for the steering motion?



My attempt at solution

1) For the first problem I think the car cannot steer due to the jets and just precesses along with the flywheel in the vertical plane.

2) For the second problem I think no resistance is offered for the turn.

Am i right? If I am not could you please correct me? I would be glad to read your responses and ideas. :smile:
 

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1) Correct, it will just precess. The angular momentum vector points along the length of the car. The only source of torque are your two jets, and that torque is perpendicular to the angular momentum, so the angular momentum vector will rotate around axis perpendicular to the wheel axis. (I'm just using the later to denote direction. They have nothing to do with the physics.)

2) The car will seem "heavier" in the turn. It will also "try" to tilt forward or backwards, which you'll notice if there is suspension.
 
Hi,

Thanks for the quick reply..:approve:

If there is no suspension (or stiff suspension) and the car is rigid and does not allow any sort of rotation along precession axis, no precession takes place. Will the car still feel heavier to turn? I think that the angular momentum cannot be conserved by precessing and if the tyres are made of undeformable rigid material unaffected by the gyro effects, resistance will not be felt. Is it right? :confused:
 
It will still seem "heavier" on a turn.
 

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