Rotational Mechanics Homework: Equations & Solution for Part 1 Work

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
1 reply · 2K views
PhysicsFuture
Messages
1
Reaction score
0

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 acceleration or velocity

Is this the right track
 

Attachments

  • upload_2018-10-28_8-21-33.png
    upload_2018-10-28_8-21-33.png
    11.7 KB · Views: 420
  • upload_2018-10-28_8-22-37.png
    upload_2018-10-28_8-22-37.png
    11.1 KB · Views: 799
  • upload_2018-10-28_8-34-28.png
    upload_2018-10-28_8-34-28.png
    2 KB · Views: 385
  • upload_2018-10-28_8-44-39.png
    upload_2018-10-28_8-44-39.png
    934 bytes · Views: 331
  • upload_2018-10-28_8-46-17.png
    upload_2018-10-28_8-46-17.png
    934 bytes · Views: 413
Last edited:
Physics news on Phys.org