No i think you're confusing horizontal and vertical... vertical suggest there is a downward force due to gravity (aka 9.81...). However, here the path is horizontal, like a merry-go-round, so there gravity does not effect the tension on a frictionless surface. since the tension must be 16 or...
if its moving in a circular horizontal path the tension isn't mg its equal to the centripetal force (mv2/r)
so I am guessing you set the centripetal force to equal 16 to solve for v. After that you can find the KE
Homework Statement
A 5 g box moving to the right at 20 cm/s makes an elastic head on collision with a 10 g box initially at rest.
Mass 1 = .005 kg
initial Velocity 1 = .2 m/s
Mass 2 = .01 kg
initial Velocity 2 = 0 m/s
a.) what velocity does each box have after the collision?
b.) what...