Help. Please...I need physics homework help. :-(.?

Question

A horizontal net force of 210 N is exerted on a 2.0 kg discus as it rotates uniformly in a horizontal circle (at arm's length) of radius 0.90m. Calculate the speed of the discus.

Answer 1

Rearrange the equation for centripetal force:
f = mv^2/r
v^2 = fr/m
v = √(fr/m)
v = √[(210)(0.9)/2.0]
v = 9.7211m/s