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Ch 10: Dynamics of Rotational Motion
Chapter 10, Problem 10

A Gyroscope on the Moon. A certain gyroscope precesses at a rate of 0.50 rad/s when used on earth. If it were taken to a lunar base, where the acceleration due to gravity is 0.165g, what would be its precession rate?

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Identify the formula for the precession rate of a gyroscope, which is given by \(\Omega = \frac{\tau}{L}\), where \(\Omega\) is the precession rate, \(\tau\) is the torque, and \(L\) is the angular momentum.
Recognize that the torque \(\tau\) is affected by the gravitational force, and can be expressed as \(\tau = mgr\), where \(m\) is the mass of the gyroscope, \(g\) is the acceleration due to gravity, and \(r\) is the radius at which the mass is concentrated from the axis of rotation.
Understand that on the Moon, the only change affecting the precession rate is the reduction in the acceleration due to gravity, which becomes \(0.165g\) instead of \(g\).
Calculate the new torque on the Moon using the modified gravity, \(\tau_{moon} = m(0.165g)r\).
Substitute the new torque back into the precession rate formula to find the new precession rate on the Moon, \(\Omega_{moon} = \frac{0.165 \tau}{L}\), and simplify using the relationship between the original torque and angular momentum.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Precession

Precession is the phenomenon where the axis of a spinning object, such as a gyroscope, moves in a circular path due to an external torque. This motion occurs perpendicular to the direction of the applied torque and is influenced by factors like angular momentum and the moment of inertia. The rate of precession can be affected by changes in gravitational force, which alters the torque acting on the gyroscope.

Torque

Torque is a measure of the rotational force applied to an object, which causes it to rotate about an axis. It is calculated as the product of the force applied and the distance from the axis of rotation. In the context of a gyroscope, the torque due to gravity affects its precession rate, and changes in gravitational acceleration, such as those experienced on the Moon, will influence this torque and thus the precession.
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Gravitational Acceleration

Gravitational acceleration is the acceleration experienced by an object due to the force of gravity acting on it. On Earth, this value is approximately 9.81 m/s², while on the Moon, it is about 0.165 times that of Earth, or roughly 1.62 m/s². The difference in gravitational acceleration affects the torque acting on the gyroscope, which in turn alters its precession rate when moved from Earth to the Moon.
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