The Gyroscope: A Wheel That Refuses to Fall

A spinning top stands up only while it spins. Mount a heavy spinning wheel in rings so its axle is free to point anywhere, and it does something stranger: pushed down at one end, it swings sideways; left alone, its axle keeps the same direction in space while the world turns under it. Johann Bohnenberger built such an instrument in 1812. Léon Foucault built his in 1852 to show the Earth's rotation without a pendulum, and named it the gyroscope — 'to view the turning'. It became the heart of compasses, autopilots and inertial navigation. This rung works out precession from the spin and the torque, and measures it on a toy gyroscope.

初学者

About 2 hours

说明

Angular momentum and precession

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Spin that stands up

A top is a gyroscope without its rings. The embedded blueprint makes one and shows why it stands only while it spins.

Measure precession against spin

Spin up a precision toy gyroscope with its pull string and set one end of its axle on the pedestal so it hangs horizontally. Time one full precession circuit with a stopwatch, and at the same moment read the rotor's spin with an optical tachometer (a strip of reflective tape on the rotor). Repeat every few seconds as it slows. Plot precession rate against spin: the product of the two stays nearly constant, as $\Omega = mgr/(I\omega)$ says. Weigh the gyroscope, measure $r$ from pivot to rotor centre, and estimate $I$ from the rotor's mass and radius to check the constant.

此步骤所需材料：

陀螺仪 - 精密金属、教学用1 个

所需工具：

秒表

数字转速表

数字厨房秤

6 英寸数显卡尺

A gyroscope that will not behave

Toy gyroscope problems.

Flow

History and honest limits

**Johann Bohnenberger** described a gyroscope-like instrument in 1812. **Léon Foucault** built his in 1852, after his pendulum, to show the Earth's rotation, and coined the name. Gyrocompasses, gyro autopilots and inertial platforms followed in the twentieth century. **Honest limits.** The precession formula assumes the spin is much faster than the precession and ignores friction and nutation. A toy gyroscope's bearings are too rough to show the Earth's rotation; Foucault's needed a very fast, very true rotor.