Rotational Mechanics Homework: Equations & Solution for Part 1 Work

Click For Summary
SUMMARY

The discussion focuses on solving a rotational mechanics homework problem involving kinetic and potential energy equations. Key equations include the total energy equation E=T+U, where T represents kinetic energy (T=1/2 mv^2) and U represents potential energy (U=∫F⋅dr). The solution involves transforming Cartesian coordinates to polar coordinates, leading to T=0.5m(r^2 + rθ^2) + 0.5M(z)^2 and U=-Mgz. The participant seeks validation for their approach, particularly in applying force balance equations for both the mass on the table and the hanging mass.

PREREQUISITES
  • Understanding of rotational mechanics principles
  • Familiarity with kinetic and potential energy equations
  • Knowledge of polar coordinate transformations
  • Ability to apply Newton's laws of motion
NEXT STEPS
  • Study the derivation of energy conservation in rotational systems
  • Learn about the application of Lagrangian mechanics in solving dynamic systems
  • Explore advanced topics in polar coordinates and their applications in physics
  • Investigate the relationship between forces and motion in multi-body systems
USEFUL FOR

Students studying physics, particularly those focusing on rotational mechanics, as well as educators looking for examples of energy conservation and force analysis in dynamic systems.

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: 410
  • upload_2018-10-28_8-22-37.png
    upload_2018-10-28_8-22-37.png
    11.1 KB · Views: 786
  • upload_2018-10-28_8-34-28.png
    upload_2018-10-28_8-34-28.png
    2 KB · Views: 373
  • upload_2018-10-28_8-44-39.png
    upload_2018-10-28_8-44-39.png
    934 bytes · Views: 317
  • upload_2018-10-28_8-46-17.png
    upload_2018-10-28_8-46-17.png
    934 bytes · Views: 398
Last edited:
Physics news on Phys.org
Please label your solution(s) with the number(s) of the part(s) that you are solving,
 
  • Like
Likes   Reactions: PhysicsFuture

Similar threads

  • · Replies 24 ·
Replies
24
Views
1K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 34 ·
2
Replies
34
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
Replies
4
Views
2K