physics
posted by Riya on .
A spoked wheel with a radius of 44.0 cm and a mass of 1.90 kg is mounted horizontally on frictionless bearings. JiaJun puts his 0.550kg guinea pig on the outer edge of the wheel. The guinea pig begins to run along the edge of the wheel with a speed of 18.0 cm/s with respect to the ground. What is the angular velocity of the wheel? Assume the spokes of the wheel have negligible mass.
rad/s
Honestly, I don't know how to calculate this, I have been trying to figure out but I have been guessing, and am sure they aren't write because they gave me wrong answers. Need help thank you in advance.

Since the bearings are frictionless, the total angular momentum of wheel and guinea pig remains zero, as they rotate in opposite directions.
0.18 m/s*0.550kg*0.44m
= 0.04356 kg m^2/s
= Iwheel*w
The moment of inertia of the wheel is
Iwheel = M*R^2 = 1.90*(0.44)^2
= 0.3678 kg*m^2. Therefore
w = 0.118 rad/s
The minus sign indicates that it is turning in the opposite direction from the guinea pig. 
Thank you so much; I really appreciate it!