The inner mass does not roll. It hangs from the rubber band, causing the mass and central portion of the rubber band to not roll, thus winding the rubber band up.Jeno said:Thank you for answering my question. But the problem is when the can rolls, the rubber band is twisted and the inner mass will also roll. thus, when the can stops, the inner mass will gain a angular velocity. it will continue to roll and this will unwind the rubber band as well. therefore, there will no any angular momentum that rolls the can back. this is, however, not match with the reality where the can really rolls back. so, can you explain why? thank you. -Jeno-
But in the experiment, the can really rolls back. So can you explain this?LURCH said:If the innner mass rolls until the rubber band unwinds, the can will not return.
But when the can is rolling and winding up the rubber band, the rubber band will unwind at the same time, with a smaller rate. Therefore, it will give both the can and the rubber band a torque in opposite direction, just like the action and reaction forces mentioned in Newton's third law. Thus, i think that the mass will roll at the same time the can rolls. Besides that, in my experiment, when i roll the can, the can will stop at a distance from me and then rolls back. but it didn't stop at the point where i roll it. it will continue rolling until a point behind me (assume that i am facing the direction where i first roll the can to). After that, it will stop at the point there and won't come back anymore. If the inner mass does not roll, then we can think that it is a simple harmonic motion where the equilibrium point is the place i start rolling the can. so the can suppose to oscillate and stop at that point finally. But it didn't match with the result of the experiment. The can just go and back one time and stop at a distance from where it start to roll. can you explain this? thank you.DaveC426913 said:The inner mass does not roll. It hangs from the rubber band, causing the mass and central portion of the rubber band to not roll, thus winding the rubber band up.
I'm not sure there's any big mystery to this. Isn't any SHM just being damped by the rolling friction and the friction of the rubber band against itself as it twists up?Jeno said:Besides that, in my experiment, when i roll the can, the can will stop at a distance from me and then rolls back. but it didn't stop at the point where i roll it. it will continue rolling until a point behind me (assume that i am facing the direction where i first roll the can to). After that, it will stop at the point there and won't come back anymore. If the inner mass does not roll, then we can think that it is a simple harmonic motion where the equilibrium point is the place i start rolling the can. so the can suppose to oscillate and stop at that point finally. But it didn't match with the result of the experiment. The can just go and back one time and stop at a distance from where it start to roll. can you explain this? thank you.
Ya, i think this is a good way, but i can't find any suitable transparent tube to do this experiment.Danger said:Why don't we just prove this empirically? Use a transparent plastic tube instead of a can, and watch what happens inside.
i think even though it is a damped oscillation, it will finally stop at the equilibrium point, except those overdamped oscillation. but the can can come back to the equilibrium point once, that means that it is not a overdamped oscillation. so why don't it stop at the equilibrium point?zoobyshoe said:I'm not sure there's any big mystery to this. Isn't any SHM just being damped by the rolling friction and the friction of the rubber band against itself as it twists up?
You could do a quick and dirty version by sticking one end of the rubber band to the bottom of a glass jar with chewing gum or Plasticene and running the other end through a hole in the lid.Jeno said:Ya, i think this is a good way, but i can't find any suitable transparent tube to do this experiment.
I had to think about this a bit. Your set up is something like an imperfect set up for SHM. Suppose you clamped a metal rod in a vise then pulled the rod back and let it go. It would oscillate with SHM. But now suppose your vise was not attached to a bench, only sitting on it. The only things preventing the vise from moving is its inertia. If you now set the rod into motion the rod will oscillate but also exert force on the vise and move it. The SHM will come to a halt very quickly and since the vise has been moved it will not be at the original position of equilibrium.Jeno said:i think even though it is a damped oscillation, it will finally stop at the equilibrium point, except those overdamped oscillation. but the can can come back to the equilibrium point once, that means that it is not a overdamped oscillation. so why don't it stop at the equilibrium point?
I think there is a misunderstanding of this experiment.Jeno said:But in the experiment, the can really rolls back. So can you explain this?
But when the can is rolling and winding up the rubber band, the rubber band will unwind at the same time, with a smaller rate. Therefore, it will give both the can and the rubber band a torque in opposite direction, just like the action and reaction forces mentioned in Newton's third law.
The rolling can with rubber band and plasticine works by utilizing the energy stored in the rubber band. When the rubber band is wound around the can, it stores potential energy. As the rubber band unwinds, this potential energy is converted into kinetic energy, causing the can to roll forward.
To make a rolling can with rubber band and plasticine, you will need a metal can, a rubber band, and plasticine or any other type of modeling clay. You may also need a pair of scissors to cut the rubber band to the appropriate length.
Yes, you can adjust the speed of the rolling can by varying the amount of tension in the rubber band. The more you wind the rubber band around the can, the more potential energy it will have and the faster it will roll.
To make the rolling can change direction, you can attach a small weight, such as a paperclip, to one side of the can. This will create an imbalance and cause the can to turn in that direction. You can also experiment with different shapes and sizes of plasticine on the bottom of the can to see how they affect its movement.
The rolling can with rubber band and plasticine can be used as a simple demonstration of potential and kinetic energy. It can also be used to model the movement of objects in physics, such as a rolling ball or a rolling car. Additionally, this experiment can be a fun and engaging way to teach children about basic principles of science and engineering.