Question

Two rollerbladers throw a frisbie back and forth on a frictionless surface. Which does not change?

a. Momentum of an individual rollerblader
b. Momentum of the frisbie
c. Momentum of the system consisting of the frisbie and rollerbladers throwing the ball
d. Momentum of the system consisting of both rollerbladers and the frisbie

I say B, am I right.

Answer 1

No. The momentum of the Frisbee changes when it is thrown and again when it is caught. Momentum conservation applies to the complete system. (d) The way you have written it, c and d are the same. I think that in (c), "rollerblader" was meant to be singular.