College

A professor holds a bicycle wheel rotating at 418 rev/min by a string attached to a weightless axle 17 cm from the wheel. The acceleration of gravity is 9.8 m/s². If all 5.5 kg of the wheel can be considered to be at its 59.1 cm radius, at what frequency (in rpm) does it precess?

Answer in units of rev/min.

Answer :

Final answer:

To determine the frequency of gyroscopic precession of a rotating bicycle wheel, one must use the gyroscopic precession equation and the known values for the wheel's mass, radius, angular velocity, and the force due to gravity to calculate the angular momentum and torque, from which the precession frequency can be derived.

Explanation:

The question given by the student pertains to the concept of gyroscopic precession in classical mechanics, a topic typically covered in college-level physics courses. Precession refers to the change in orientation of the rotational axis of a spinning object, in this case, a bicycle wheel. To solve the problem, we must use the equation for gyroscopic precession, which is given by = rac{L}{ au}, where is the precession frequency, L is the angular momentum of the wheel, and au is the torque acting on the wheel.

The angular momentum L can be found using the formula L = I * _0, with I being the moment of inertia and _0 being the initial angular velocity of the wheel. Since the wheel’s mass distribution is given as being concentrated at its radius, I = mr^2, where m is the mass of the wheel and r is the radius. The initial angular velocity _0 (in radians per second) is obtained by converting the given rotational speed from revolutions per minute to radians per second. Torque au is calculated by the product of the force due to gravity (the weight of the wheel) and the distance from the axis of rotation, au = r * F_gravity, with F_gravity = m * g, where g is the acceleration due to gravity.

After calculating L and au, one can find the precession frequency . To convert the answer back to revolutions per minute for the frequency of precession, it must be multiplied by the conversion factor of 60/2 au (since 1 rad/s = 60/(2 au) rev/min).