# I need to to find the moment of inertia for the system

1. Nov 19, 2008

### afcwestwarrior

1. The problem statement, all variables and given/known data

2 kg uniform rod of length 1m is constrained to rotate about a horizontal axis passing through its center. The rod has a 1.5 kg point mass attached to one end and a 0.5 kg point mass attached to the other end. The 1.5 kg mass is given a downward push so that it starts moving with an initial velocity of 1.2 m/s.

Ok I used the equation of moment of inertia or rotational inertia
I=m(r)^2

Here's what I did
m1=.5 kg
m2=1.5 kg
M=2kg
r=1/2 because L =1m and the center of mass is in the middle of the rod
thus I plugged in the variable

I=.5(1/2)^2 +1.5(1/2)^2
=.5 kg*m^2

is that right

and next i have to find the initial kinetic energy and then i have to find the total angle of it coming to rest. I need help

2. Nov 20, 2008

### tiny-tim

Hi afcwestwarrior!

(have an omega: ω )

Yes, your I is right … but don't forget to add on the I of the rod itself!

Now use rotational KE = (1/2)Iω2,

and PE + KE = constant.