The discussion centers on the concept of tension in a rope when there is no acceleration, specifically in the context of Newton's laws of motion. Participants clarify that tension can exist even when acceleration is zero, as illustrated by scenarios like tug of war, where opposing forces create tension without movement. The correct formulation of the relationship between forces is Σf=ma, emphasizing that net force determines acceleration. The conversation highlights the importance of understanding forces acting on the rope and introduces the concept of stress as a function of tension and cross-sectional area.
PREREQUISITESPhysics students, educators, engineers, and anyone interested in understanding the dynamics of forces and tension in mechanical systems.
well , we don’t give answers, but here’s A hint: in the equation f= ma, f is the net force acting on the rope. So if a is 0, net force is zero, and if the car is pulling with a force on the rope, there must be another force acting on the rope to give a net force of 0. What is it? Surely you’ve seen a vehicle trying to pull another out of the mud, and neither vehicle is moving in spite of the first one with pedal to the floor, and the rope is pretty tight , right?Pi-is-3 said:
This description is most unclear.sumitsumit said:
Does the car suddenly go from stationary to speed v? How does it "start to move" with no acceleration?Pi-is-3 said:
I have no idea how it starts. I didn't start the thread @sumitsumit did. Honestly I am more confused by what @PhanthomJay said.haruspex said:
The correct equation is Σf=ma, i.e. the acceleration results from the sum of all forces. The tension in the rope is only one force on the car; there may be others.Pi-is-3 said:
Well perhaps here is a better example...a game of ‘tug of war’. Your team is pulling on one end of the rope, trying to move the opposing team. And the opposing team is pulling the rope on the other end, trying to move your team. But assume strengths and foot holds of each team are the same, so no one is going anywhere. It’s a stalemate. There is no acceleration. Now you are trying to tell me there is no tension in the rope? There is a lot of tension , the rope might be close to breaking if it’s not strong enough. Think about Newton’s first law and draw a free body diagram of the rope from one end to an imaginary cut in-the center.Pi-is-3 said:
Now I get it. Thanks!PhanthomJay said:
Please tell me that you believe that you can’t have a force without acceleration.Pi-is-3 said:
