By no means this is a complete notes.
It is a vector. Symbol is L
Unit: kg m²/s
When an object spins, it gains angular momentum. In that case, the object has inertia and keep spinning, resisting other force from interrupt (e.g. Gravity).
For example, a bicycle will not fall if it is cycling with sufficient speed.
There are two types of angular momentum. Point object and extended object.
Object rotating (or spinning) around a given point.
For example, planet, electron in an atom, string plus a mass.
L = r * p = r * m * v
Where v is the linear velocity. Similar to circular motion.
Whole object rotating around a point. For example, gyroscope.
L = I * ω
Where:
- I is rotational inertia of the object
- ω is the angular speed of the object
Use right hand rule. Similar to magnetic field from a coil.
4 fingers pointing to rotate direction and the thumb direction is direction of T.
Similar in linear momentum. Where F(avg) * t = Δp
For angular momentum, ΔL = net torque * Δt
Using a turntable (those in 酒樓). This would generate angular momentum on extended object.
Attach photo gate on the turntable to measure angular velocity of the table.