I Virtual work and constraint forces

AI Thread Summary
In a system of N particles with constraints, performing a virtual displacement on one particle can cause other particles to move in response. The inquiry focuses on calculating the virtual work done by constraint forces on all particles involved, questioning whether a non-zero result is possible for the work done on the single particle. The discussion references a book that states the total virtual work done by all particles must equal zero, in accordance with the principle of virtual work. However, it clarifies that the work done on an individual particle does not necessarily have to be zero. The principle emphasizes that while the net virtual work is zero, individual contributions may vary.
Ahmed1029
Messages
109
Reaction score
40
Suppose I'm considering a system of N particles that are constrained in their possible motions and so there are less that 3N generalized coordinates. Suppose now I perform a virtual displacement on one particle, which due to some constraints might force some other particles to more virtually with it, like the case of an atwood machine. I now want to calculate the virtual work done by the constraint forces on the particles that move as a corrolary to the movement of this single particle plus the work done on this particle itself, can I get a non-zero result? I'm asking because the book I'm reading assers that the virtual work done by virtually moving ALL the particles has to be zero, and not necessarily the work done to move a single particle has to be zero.
 
Physics news on Phys.org
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...
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?
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...
Back
Top