Rotational Mechanics Homework: Equations & Solution for Part 1 Work

AI Thread Summary
The discussion focuses on solving a rotational mechanics homework problem involving energy equations and free body diagrams (FBD). Key equations include the total energy E as the sum of kinetic energy T and potential energy U, with specific expressions for T in both Cartesian and polar coordinates. The potential energy U is defined as -Mgz, and the relationship between z and r is established as z = L - r. The FBD analysis for both the mass on the table and the hanging mass leads to equations for centripetal force and acceleration. The participant seeks confirmation on their approach and calculations for the problem.
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Homework Statement


upload_2018-10-28_8-22-37.png


Homework Equations


E=T+U
T=1/2 mv^2
U=∫F⋅dr

The Attempt at a Solution



Part 1 Work
x=x-dot
y=y-dot
z= z-dot
r=r-dot
θ=θ-dot
[/B]
T= 0.5m(x^2 +y^2) 0.5M(z)^2
Changing to polar coordinates
T=0.5m(r^2 +rθ^2) 0.5M(z)^2

U=-Mgz

E=T+U
=0.5m(r^2 +rθ^2) 0.5M(z)^2-Mgz

z=L-r

= 0.5m(r^2 +rθ^2) 0.5M(z)^2-Mg(l-r)


I drew the FBD for both:
for mass on table
upload_2018-10-28_8-34-28.png

Fx
Fc-T=ma

Fc= mrw^2
T=Mg
mrw^2-Mg=ma

a=
rw^2-(Mg)/m
v=rw^2-(Mg)r/m

for hanging mass
upload_2018-10-28_8-44-39.png


Fc-Fg=0
Fc=Fg
Fc=Mg

No accleration or velocity

Is this the right track
 

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