# Forces on bar

1. Dec 3, 2007

### roldy

1. The problem statement, all variables and given/known data
The 2 kg rod AB and the 3kg rod BC are connected as shown to a disk that is made to rotate in a vertical plane at a constant angular velocity of 6 rad/s clockwise. For the position shown, determine the forces exerted at A and B on rod AB.

2. Relevant equations
summation of forces
mass moment of inertia
relative velocites and accelerations

3. The attempt at a solution
I think I solved the accelerations and angular accelerations correctly but at this point I'm unclear as to what to do next.

2. Dec 3, 2007

### Gokul43201

Staff Emeritus
Looks good so far!

You accidentally set the wrong component to zero in the line for a_A, but you fixed it in the next line. Make sure you correct that line too!

Now that you have a_A and a_B, throw away everything except rod AB. You can now describe the dynamics of rod AB in terms of a center of mass acceleration (=(a_A+a_B)/2) and an angular acceleration about the center (=(a_A-a_B)/L). This can be seen as coming from a pure force (acting at the center) and a pure couple (torque about the center). From here, finding the forces at A and B is just a matter of adding and subtracting.