Practice!

Sample Problem

Somebody leaves a pen weighing 15 grams on the edge of a 30 centimeter record spinning at 45 rpm on a record player, and that the pen has a velocity of 1.4 m/s. What is its angular momentum?

Nms

Solution

We will use the formula L = rmv. We know m = .015, that r = .30, and that v = 1.4. We plug all of these values into the formula and get that L = (.30) (.015) (1.4) = .0063 Nms.