Main Question or Discussion Point
This is more of a genral question i want apply to a problem i am working on. If i was standing on a cart with four wheels an i am holding a string that is wound around the axel of the back wheels. So as i pull the string it unravels around the back axel turning the axel and moving the cart. I want to find the tourque that this is putting on the axel. So i am looking for some advice on how to attack this. I would know how much force i am pulling up on the string with. but would i also need to know the mass moment inertia of the wheels and the friction between the wheels and the ground so i know what i have to over come to get the cart moving. Because right when i start pulling on the string its going to put a greater torque on the axel because it has to overcome static friction and inertia but then once it is moving the torque will be less because the only thing resisting motion is kinetic friction. So i am looking for ideas on how to model this.