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**DISCUSSION THREAD**

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**Discussion**

**FOUR-STEP PLAN**

* Step 1: FBD* - Draw

*individual*free body diagrams of A and B, along with an FBD of pulley C.

* Step 2: Newton* - From each FBD, write down the Newton's equation for components along the incline. Recall that the pulley has negligible mass.

* Step 3: Kinematics* - You will need to use the cable-pulley system kinematics that we worked with earlier in the semester. Please review the material from Section 1.D of the lecture book to relate the accelerations of blocks A and B.

* Step 4: Solve *- Combine your equations from Steps 2 and 3 to solve for the accelerations of blocks A and B.

How are you supposed to approach this problem? I tried to start by drawing a FBD for block A and B, but how do you figure out the tension forces that the ropes are exerting? Or should you do kinematic analysis with the ropes first before moving on to forces?

The pulley's are massless, and inextensible cables have a constant reaction force throughout the cable. That should help.

How do you write the acceleration equation for the pulley if it has no mas? Do you simply sum the forces to 0 because no mass = no net force?

Yes, that is correct. Since m = 0, then m*a = 0.

Is it necessary to use the Cable Kinematics for this problem? When I solved it, I created a FBD for both blocks and the pulley and then was able to solve for acceleration of both blocks from those. I’m not sure if this method makes sense for this type of problem.

I am confused on this problem - I know the forces are supposed to be the same across the pulley and that I have to use the pulley equation to find the ratio of one acceleration to the other, but how would I find any number to start with? I can solve for one in terms of the other, but I don't know how I can solve for one in the first place.

Are we supposed to infer that the tension forces being exerted by the cables in the positive x direction on Box A is the same force that's being acted in the negative x direction?