rotational speed Definition and 52 Threads

I want to measure the rotational speed of Io using a spectrograph, using the doppler formula. Since it is rotating around Jupiter, i have to take the velocity relative to jupiter, but I wonder tough how this is possible when Io is not rotating at an right angle to my observation point. Is there...

Here is the question: The speed of a moving bullet can be determined by allowing the bullet to pass through two rotating paper disks mounted a distance 0.921 m apart on the same axle. From the angular displacement 27.4 degrees of the two bullet holes in the disks and the rotational speed...