Problem - Different weights on a swinging rod

AI Thread Summary
The problem involves a wooden rod pivoted at its center with a rat and a mouse at each end, requiring the calculation of their speeds as the rod swings vertically. The solution can be approached using energy conservation principles, equating the initial potential energy to the kinetic energy at the vertical position. However, applying Newton's second law directly is insufficient for this rotating system, as torque must also be considered. To solve it dynamically, one must account for the rotational motion and the forces acting on the system. Understanding these concepts is crucial for accurately determining the speeds of the animals as the rod swings.
brotherbobby
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The following problem is from Sears and Zemansky's textbook.

A wooden rod of negligible mass and length 80.0 cm is pivoted about a horizontal axis through its center. A white rat with mass 0.500 kg clings to one end of the stick, and a mouse with mass 0.200 kg clings to the other end. The system is released from rest with the rod horizontal. If the animals can manage to hold on, what are their speeds as the rod swings through a vertical position?

The problem can be done using energy conservation (K_1+U_1 = K_2+U_2). You take the total energy of the system at start when the rod is horizontal and equate it to the total energy of the system when the rod is vertical.

But I have not been able to do the problem using Newton's second law (F = m d^2x/dt^2). Any guess as to how to go about it?
 
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I believe you posted in the wrong section.
Btw it's a rotating system, so if you want to solve it dynamically you'll need to make use of torque, not just Newton's 2nd law.
 

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