Conservation of angular momentum of an an engine flywheel

In summary, when the engine flywheel and clutch plate are pushed together without applying any torque, their moments of inertia and angular speeds will eventually become equal due to the conservation of angular momentum.
  • #1
henry3369
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Homework Statement


Figure 10.30 shows two disks: an engine flywheel (A) and a clutch plate (B) attached to a transmission shaft. Their moments of inertia are and initially IA and IB, they are rotating with constant angular speeds ωA and ωB, respectively. We push the disks together with forces acting along the axis, so as not to apply any torque on either disk. The disks rub against each other and eventually reach a common angular speed Derive an expression for ω

Homework Equations


Conservation of angular momentum

The Attempt at a Solution


I'm confused about why angular momentum is conserved here. When the flywheel comes in contact with the clutch, isn't there friction before the two begin moving with the same speed, which is an external force that contributes to the torque of the system; thus, momentum would not be conserved? Is friction ignored because I am only looking at two moments in time: when the clutch and flywheel aren't in contact and after the two are rotating together?
 
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  • #2
The friction is a force that's internal to the system under consideration, so no external torques are involved.

The linear analogy is the perfectly inelastic collision where energy is lost to heat, sound, etc., yet momentum is still conserved.
 

1. What is conservation of angular momentum?

Conservation of angular momentum is a fundamental law of physics that states that the total angular momentum of a system remains constant, unless acted upon by an external torque. In simpler terms, this means that the rotation of an object will remain constant unless a force is applied to change it.

2. How does the conservation of angular momentum apply to an engine flywheel?

In an engine, the flywheel is responsible for maintaining the rotational momentum of the engine. This momentum is necessary to keep the engine running smoothly and to prevent it from stalling. The conservation of angular momentum ensures that the flywheel will continue to rotate and keep the engine running, even when there are fluctuations in the torque applied to it.

3. What factors affect the conservation of angular momentum in an engine flywheel?

The conservation of angular momentum in an engine flywheel is affected by the mass and distribution of the flywheel, the speed at which it is rotating, and any external forces acting on it. The larger the mass and the faster the rotation, the greater the angular momentum will be. Any external forces, such as friction or air resistance, can also affect the conservation of angular momentum.

4. Can the conservation of angular momentum be violated?

No, the conservation of angular momentum is a fundamental law of physics and cannot be violated. This law has been extensively tested and has been shown to hold true in all observed cases. However, in certain situations, it may appear that angular momentum is being violated. This is due to the fact that the conservation of angular momentum takes into account the entire system, including any external forces acting on it.

5. How is the conservation of angular momentum used in engine design?

The conservation of angular momentum is a crucial factor in engine design. Engineers must consider the mass, distribution, and speed of the flywheel when designing an engine to ensure that it has enough rotational momentum to keep the engine running smoothly. They must also take into account any external forces that may affect the conservation of angular momentum in the flywheel. Additionally, the principles of conservation of angular momentum are used in other engine components, such as the crankshaft and pistons, to ensure the smooth functioning of the engine.

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