Question about gravitational potential energy and angular motion

AI Thread Summary
The discussion centers on understanding gravitational potential energy and angular motion in a homework context. The user has derived expressions for initial and final energy, questioning the use of potential energy in different scenarios. Confusion arises regarding the relationship between linear velocity (v) and angular velocity (ω) at a specific angle (θ), as well as the moment of inertia (I) in relation to mass (M), radius (a), and length (l). Participants emphasize the need to clarify which energy expressions apply in each situation and the importance of defining the axis for moment of inertia. The conversation highlights the complexities of energy conservation in rotational dynamics.
plomeiko
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Homework Statement
all below
Relevant Equations
all below
hello I would like some help with the first part of this homework.
for the moment i have done this:
E initial=m*g*h
Efinal= 1/2 m*v ^ 2+1/2I*ω ^ 2

Ei=m*g*h+1/2I*ω ^ 2
Ef=1/2*m*v ^ 2

my doubt is with the potential energy since it confuses me when there is or not

https://www.physicsforums.com/attachments/268784
 
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plomeiko said:
E initial=m*g*h
Efinal= 1/2 m*v ^ 2+1/2I*ω ^ 2

Ei=m*g*h+1/2I*ω ^ 2
Ef=1/2*m*v ^ 2
You have two expressions for Ei and two for Ef. How come? Which pair applies?
When at angle θ, what is the relationship between v and ω?
What is I in terms of M, a and l?
 
the first pair is when it reaches the angle θ and the second when it falls from the table.
and the letter I is inertia

is it wrong?
 
plomeiko said:
the letter I is inertia
Yes, but about which axis?
And I ask again
haruspex said:
When at angle θ, what is the relationship between v and ω?
 
plomeiko said:
Homework Statement:: all below
Relevant Equations:: all below

hello I would like some help with the first part of this homework.
for the moment i have done this:
E initial=m*g*h
Efinal= 1/2 m*v ^ 2+1/2I*ω ^ 2

Ei=m*g*h+1/2I*ω ^ 2
Ef=1/2*m*v ^ 2

my doubt is with the potential energy since it confuses me when there is or not

https://www.physicsforums.com/attachments/268784
The attachment appears to be missing now. Can you attach it again?
 
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