1. Compound Body Problems

2. Required Steps
Identify the variable(s) the problem asks you to calculate.
Draw FORCE DIAGRAM (or two FBD’s, or three FBD’s, or…)
Write the “Compound Body Version” 2nd Law (or the expanded 2nd Law formulas, one for each FBD)
Substitute given or computed values into the formula
Solve for acceleration
Make FBD for on part, write expanded 2nd law, sub and solve for internal (to the system) force

3. Ex1: Atwood Device
Determine the acceleration of the masses and the tension in the string.
Assume the pulley is massless
And frictionless. 1 2
10.0 kg
3.33 kg

4. Ex 2: Modified Atwood Device
The block on the table is 5m, and the hanging block is m. Assuming no friction and a massless pulley, compute the acceleration of the system, and the tension in the string. 2 1

5. Ex 3 (String & Incline & Pulley, Oh My!)
Determine the acceleration of the system, and tension in the string. The slope is 30.0° and the masses are 1.00kg and 3.00kg. (assume no friction and massless pulley) 2 2 1

6. Ex 3
Determine the minimum coefficient of static friction if the blocks remain at rest. The slope is 30.0° and the two masses are 1.00kg and 3.00kg.

7. Ex 3 Cont.
Determine the coefficient of kinetic friction if the blocks slide at a constant speed. The slope is 30.0° and the two masses are 1.00kg and 3.00kg.