Posted by AP Physics B on .
can you check my reasoning
1. The problem statement, all variables and given/known data
ok well then...
we did a lab were you have a hanging mass attached to a stirng that went through a straw and was attached to a rubber stopper. The lab was to find the mass of the rubber stopper once you know the velocity. So I was woundering if this looks correct
2. Relevant equations
f = ma
m1 = mass of stopper
m2 = mass of hanging mass
radial acceleration = r^1 v^2
3. The attempt at a solution
net force radial = m (acceleration radial) = force of gravity on mass m2
net force radial = (m1 + m2) (acceleration radial) = m2 g
net force radial = m1(acceleration radial) + m2 (acceleration radial) = m2 g
net force radial = m1(acceleration radial) = m2 g  m2 (acceleration radial)
divided both sides by acceleration radial
m1 = (acceleration radial)^1 ( m2 g  m2 (acceleration radial) )
at which point I plugged in the value I found for the radius
the value I found for the period
and found the radial acceleration

AP Physics B 
bobpursley,
Not if I understand what you did. a mass m1 was spun horizontally, and tied to a hanging mass m2. IF that is true, then
radial force=hanging force
m2 v^2/r=m1g
I don't understand what you did. 
AP Physics B 
AP Physics B,
why would the hanging mass of a radial acceleration if it\'s just in equilibrium...???
m1 V^2/r = m2 g 
AP Physics B 
AP Physics B,
I did this
net force = (m1 + m2) (radial acceleration of mass m1) = force of gravity on mass m2 
AP Physics B 
bobpursley,
What was the experiment setup? Was m1 rotating horizontally? Was m2 a hanging mass attacahed to the cord holding the rotating mass?

AP Physics B 
AP Physics B,
mass m1 was a robber stooper
m1 was attached to a string that went through a straw
on the other end of the straw the string came out and was attached to a mass m2
students spun mass m1 with hand on straw as the stopper spun around mass m2 the hanging mass was in equilibrium as mass m1 the stopper spun around in a circle and experienced a radial force 
AP Physics B 
bobpursley,
Then m2 was as I thought, it was supplying the tension counter centripetal force.
m2*g=m1*v^2/r