# Measuring parallel velocity in rotating frame.

1. The problem statement, all variables and given/known data
At t=0 a police officer is located at (0,R) on a circular platform whose radius is R and which rotates around the z axis with constant angular velocity ω. The officer’s velocity at that point in time is (ωR ,0). At that time, a bird leaves the center of the platform along the x axis with constant velocity (v0,0). The officer is equipped with a laser velocity-meter which measures the velocity parallel to the beam. The officer aims the device at the bird. What would be the velocity of the bird as detected by the officer?

2. Relevant equations

3. The attempt at a solution
The officer’s velocity should be (I think):
Vofficer = ωR(-sin(ωt),cos(ωt)). However, I am not sure what the bird’s velocity would be. In the lab’s reference frame the bird would obviously be moving in a straight line. Moreover, if in the rotating reference frame its velocity is constant then wouldn’t its velocity simply be: v0(-sin(ωt),cos(ωt))? I am quite sure this is wrong, but I am making an effort. I’d appreciate some help with this.

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