What are the other forces acting on ##dm## in addition to gravity?

AI Thread Summary
The discussion focuses on analyzing the forces acting on a mass (dm) in addition to gravity. The main forces identified are tension and the weight of dm, with calculations yielding different tangential accelerations when using energy conservation versus torque methods. The calculated tangential acceleration using centripetal force is 5.9 m/s², while the torque method provides 8.82 m/s², indicating a potential error in resolving forces. Additionally, the role of the rod's upper section is highlighted, as it exerts a tangential force on dm that needs to be considered. Understanding these forces is crucial for accurate calculations in dynamics.
Vivek98phyboy
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Homework Statement
A uniform rod of length L pivoted at its upper end hangs vertically. It is displaced through an angle of 60° and then released. Find the magnitude of the force acting on a particle of mass 'dm' at the tip of the rod when the rod makes an angle of 37° with the vertical.
Relevant Equations
Tangential acceleration of tip(dm), a= L𝛂
After solving using energy conservation, I found the angular velocity at 37° to be omega=2.97/(L)^½

IMG_20200806_184138.jpg


Tension and the weight (dm)g are the two forces acting on the tip dm
To find the resultant force, I resolved the centripetal force and tangential force to find the centripetal force as
F= (dm)(L)(omega)²
and tangential force as (dm)(g)sin37°.
This would leave me with a tangential acceleration of 5.9 m/s²
But when I calculated it using torque, I found the tangential acceleration to be 8.82m/s² and that is the solution given in my book

What am I doing wrong while resolving the forces?

I would also like to know what would be the forces provided by the part of rod that is above 'dm'?
 
Physics news on Phys.org
The force of gravity is not the only force on ##dm## that has a tangential component. The force that "binds" ##dm## to the rod also has a tangential component.
 
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