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Finding angular acceleration from following information- torque and rotational I?

  • #1

Homework Statement


The figure shows a view from above of two objects attached to the end of a rigid massless rod at rest on a frictionless table. Imagine a vertical rod, on the top end is a mass of m, an the bottom is a mass of 2m. The length of the rod is L and L/4 down from m (at top), a horizontal and rightward force is applied. When this F is applied, the resulting rotational acceleration of the rod about its center of mass is kF/(mL).


Homework Equations


What is K?


The Attempt at a Solution


So I found the center of mass as 2/3 L below mass m. but I don't understand how we can get torque (like I know its r cross F), but.. We can use torque=I times angular acceleration. But i got I wrong. HELP! please!
 

Answers and Replies

  • #2
oh! is it just because torque equals r cross f and that means it equals 2/3 L- 1/4 L?
 

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