Inverse Dynamics - 2 Rigid Bodies connected with hinge

AI Thread Summary
The discussion focuses on simulating inverse dynamics for two rigid bodies connected by a hinge. The initial calculations for torque used the formula τ=Iα for a single rod, and then applied the parallel axis theorem for a rod fixed at a hinge. The user is now uncertain about how to calculate the torque for the second rod attached to the first, particularly regarding the interaction between the two rods and whether there is a negative torque involved. They have disabled gravity for the simulation and are seeking insights on these dynamics. Understanding Lagrangian dynamics may provide additional clarity for the calculations involved.
leonj
Messages
1
Reaction score
0
I am trying to simulate and animate inverse dynamics. So I need to calculate torques. I started out by just taking a rod which rotates about its COM, applied a torque and then just used \tau=I\alpha to make sure I get back the same torque I applied. Next, I attached the rod to the ground with a hinge joint. This time to get the torque I used the parallel axis theorem to get \tau=(I_{COM}+Mh^2)\alpha. So my next step is to attach a second rod to the end of the one attached to the ground. What I am stuck on now is I am not sure how the two rods interact.

For example how do I calculate the torque on the rod connected to the ground? When it is just one rod I used the aforementioned \tau=(I_{COM}+Mh^2)\alpha, but now with the other rod attached to it, what else do I need to take into account? Is there a negative torque on the opposite side?

Note: For now I have disabled gravity.

I would appreciate any insight. Thanks
 
Physics news on Phys.org
If you are not familiar with Lagrangian dynamics, this would be a good excuse to do so.
 

Thread '1:1 versus 2:1 Mechanical Advantage debate'

The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
View full post »

Thread 'Newton's first law?'

Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
View full post »
Thread 'Beam on an inclined plane'

Thread 'Beam on an inclined plane'

Hello! I have a question regarding a beam on an inclined plane. I was considering a beam resting on two supports attached to an inclined plane. I was almost sure that the lower support must be more loaded. My imagination about this problem is shown in the picture below. Here is how I wrote the condition of equilibrium forces: $$ \begin{cases} F_{g\parallel}=F_{t1}+F_{t2}, \\ F_{g\perp}=F_{r1}+F_{r2} \end{cases}. $$ On the other hand...
View full post »

Similar threads

A doubt in the rotational analogue of F=ma
Replies
3
Views
2K
Euler Equations for Dynamics of rigid body
Replies
5
Views
2K
I Why does a free rigid body rotate only about its COM when F(ext) is applied?
Replies
7
Views
1K
I Conservation of angular momentum during collisions
Replies
3
Views
3K
Rod with Current on Rails in Magnetic Field
Replies
12
Views
1K
I Where is the centripetal force acting on mass M?
Replies
21
Views
2K
Projectile motion of a two-point rigid body
Replies
8
Views
2K
Torque and Moment of Inertia of a Lever Arm
Replies
2
Views
3K
A Modeling the damping of a physical rigid pendulum
Replies
1
Views
2K
Conserving Angular Momentum (Rigid Body Dynamics)
Replies
3
Views
3K

Hot Threads

Recent Insights

Back
Top