Centripetal Motion Lab

Assume that you've hung a mass MH from a string and
on the other end is a stopper of mass MS swinging
around in a horizontal circle.  If there is no friction on the
string, then the tension on the string pulling MH up
equals the tension on the string pulling MS  inward, i.e.,
providing the centripetal force.

The tension up on MH equals its weight - because its
acceleration is zero, thus T = W = MH *g

The tension inward on MS = Fnet because it is the
ONLY force on the stopper in the horizontal direction.  Thus
T = Fnet = MS*a = MS * (v2/R)
- recall that this is the formula for centripetal acceleration.

To connect to the experiment, the only other formula we need is the
one rrelating the time to go around to the speed v.
v = (distance) / (time) = (2 * Pi * R) / (t)