How Do You Calculate Arc Length and Angle Measurements in Circular Motion?

[8parks11]

A protractor is made so that the edge of its scale is 7.5 cm from the center point. If the scale is marked in degrees, how far apart are the marks along the edge?

I just thought this would be 360/7.5 but it's not. I'm not sure If I got the question correct.





A 12-inchdiameter phonograph record rotatesaboutits center by one-quarter turn. a) Thorugh how many radians has it turned? b) How far has a point on the rim moved?

For a, I got pi/2 which I think iscorrect, but for b, I don't know what to do...

 

[8parks11]

can i get some help?

 

[OlderDan]

What is the circumference of a circle in terms of its radius?