Non-ideal atwood machine problem

[jacker2011]

[SOLVED] non-ideal atwood machine problem

Homework Statement

Atwood machine.
mass a is 19kg and mass b is 9 kg
the pulley itself has diameter of 15cm and mass of 41kg
mass A and b are release from rest. How far does mass A move in 2 sec?

Homework Equations

I = 1/2 mr^2

The Attempt at a Solution

 

[jacker2011]

really stuck at this non-ideal pulley problem..please help due tomorrow

 

[jacker2011]

I came up with two equation, but not sure if it is correct:
Ta(0.0075) + Tb(0.0075) = 1/2mr^2a
Total energy= 1/2mv^2 +1/2W^2+ mgh
What shall I do first? Find the acceleration of the two objects?

 

[jacker2011]

really need help in this

 

[Doc Al]

To find the acceleration, analyze the situation using Newton's second law, not conservation of energy.

You'll need three equations: one for mass a, one for mass b, and one for the pulley.

Analyze the forces on each object separately and apply Newton's 2nd law. Combine those three equations to solve for the acceleration.

 

[jacker2011]

ohh alright thanks!

 

[jacker2011]

wait, equation for what? solving for acceleration?
so i find 3 equations of acceleration for mass a, b and pulley?

 

[jacker2011]

first i guess all the acceleration is the same for pulley, mass A, and Mass B
i set them equal to each other and solve for acceleration

so the acceleration is 2.02m/s^2

 

[Doc Al]

Looks about right.