Question

The 480 g bar is rotating as shown what is the angular momentum of the bar about the axle?

Answer 1

On a similar problem wherein instead of 480 g, a 650 gram of bar is used:

Angular momentum L = Iω, where 
I = the moment of inertia about the axis of rotation, which for a long thin uniform rod rotating about its center as depicted in the diagram would be 1/12mℓ², where m is the mass of the rod and ℓ is its length. The mass of this particular rod is not given but the length of 2 meters is. The moment of inertia is therefore 
I = 1/12m*2² = 1/3m kg*m² 

The angular momentum ω = 2πf, where f is the frequency of rotation. If the angular momentum is to be in SI units, this frequency must be in revolutions per second. 120 rpm is 2 rev/s, so 
ω = 2π * 2 rev/s = 4π s^(-1) 

The angular momentum would therefore be 
L = Iω 
= 1/3m * 4π 
= 4/3πm kg*m²/s, where m is the rod's mass in kg. 

The direction of the angular momentum vector - pseudovector, actually - would be straight out of the diagram toward the viewer. 

Edit: 650 g = 0.650 kg, so 
L = 4/3π(0.650) kg*m²/s 
≈ 2.72 kg*m²/s