How Can Angular Velocity Be Expressed as a Function of Theta for a Falling Rod?

Click For Summary
SUMMARY

The discussion focuses on deriving the angular velocity of a uniform rod as it falls, specifically expressing it as a function of the angle Theta with the vertical. The moment of inertia is calculated as Ic = (ml^2)/3, and the torque is defined as Torque = mgd, where d = asin(theta). The angular acceleration is derived as Angular Accel = 3/(4a) * gsin(theta). The main challenge is substituting angular acceleration to find an equation for angular velocity, leading to the integral W = Integral [ 3/4 * 1/a * gsin(theta) ] dt.

PREREQUISITES
  • Understanding of rotational dynamics and torque
  • Familiarity with the concepts of angular velocity and angular acceleration
  • Knowledge of calculus, particularly integration
  • Basic principles of mechanics involving rigid bodies
NEXT STEPS
  • Study the relationship between angular acceleration and angular velocity in rotational motion
  • Learn about the integration of functions in the context of physics, specifically for angular motion
  • Explore the application of the conservation of energy in falling objects
  • Investigate the use of differential equations in modeling angular motion
USEFUL FOR

Physics students, mechanical engineers, and anyone studying dynamics and kinematics of rigid bodies will benefit from this discussion.

moo5003
Messages
202
Reaction score
0
Question:
"A uniform rod of mass m and length 2a stands vertically on a rough horizontal floor and is allowed to fall. Assuming that slipping has no occurred, write the angular velocity of the rod as a function of the angle Theta the rod makes with the vertical."

WORK DONE:
Ic = (ml^2)/3
Torque = mgd
d = asin(theta)
Torque = angular accel * I

mgasin(theta) = ang accel * (ml^2)/3
l = 2a

gasin(theta) = ang accel * (m(2a)^2)/3
gsin(theta) = 4/3 * ang acell * a

Ang Accel = 3/(4a) * gsin(theta)

MAIN QUESTION: How do I substitute Angular Acceleration such that I can find an equation that solves angular velocity?
 
Physics news on Phys.org
Angular acceleration [itex]\alpha\,=\,\dot\omega\,=\,\ddot\theta[/itex]

Angular velocity [itex]\omega\,=\,\dot\theta[/itex]
 
Astronuc said:
Angular acceleration [itex]\alpha\,=\,\dot\omega\,=\,\ddot\theta[/itex]
Angular velocity [itex]\omega\,=\,\dot\theta[/itex]

I considered using calc to solve for this. But the integral of Angular Acceleration is a function of time. I'm unsure how I can incorporate that together and produce an equation as a function of Theta.

W = Integral [ 3/4 * 1/a * gsin(theta) ] dt

Would I just slap on a variable T and give that as my answer (There is no initial angular velocity right)? Or can I somehow subtitute T as a function of Theta?
 
Last edited:

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
Replies
67
Views
5K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
10
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
Replies
15
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
12
Views
2K
  • · Replies 4 ·
Replies
4
Views
8K
Replies
5
Views
9K