The discussion revolves around a problem involving a 2.5 kg rubber ball rolling across dry concrete with an acceleration of 4.0 m/s². Participants are tasked with determining the frictional force required to stop the ball, but the problem statement raises several ambiguities regarding the conditions of the scenario.
The discussion is ongoing, with multiple interpretations being explored. Participants have raised concerns about the ambiguity of the problem and have suggested that the original poster clarify the question. Some guidance has been offered regarding the distinction between kinetic and static friction, but no consensus has been reached on how to proceed with the problem.
There is uncertainty about the conditions under which the ball is rolling, whether the surface is horizontal, and the timeframe or distance over which the ball should stop. Additionally, the relevance of the coefficient of friction provided is under scrutiny, as it may not apply to the situation described.
it doesn't say if the speed is consistent or speeding up. I'm confused when they add the acceleration to the question. so I'm assuming you find the net force (2.5 kg)(4.0 m/s^2[E], first I'm not sure if that's where to start and if that's correct what would the next step be?gneill said:Hi joelm.
Please note that the rules require that you show an attempt at solution before help can be offered. What have you tried?
Is the problem statement word-for-word as it was given to you? Is the ball really speeding up (the acceleration you stated is positive)?
Yea I'm really confused as well. Would Fnet (Net force) = Normal force? They give you the formula Ff= (u)(Fn) u= coefficient Fn= normal forcegneill said:As stated, the problem is rather ambiguous. The ball is said to be rolling, so I don't see how kinetic friction would apply or why its coefficient would be given. They don't say why it is accelerating. They don't say if the concrete surface is horizontal or not. They don't say how the ball should come to a stop, whether in some particular timeframe or over a particular distance. So I can't offer any suggestions other than that you find the force as you've done.
Yes for sure. This is exactly as worded.Cutter Ketch said:I think what gneill is saying is that you may have mangled the question in your post. It doesn't seem to make much sense. Could you try posting the question again being careful to state it exactly as given?
joelm said:Yes for sure. This is exactly as worded.
If a 2.5 kg rubber ball is rolled across the dry concrete floor with an acceleration of 4.0 m/s^2 [E]. Determine the friction force required to stop the ball. ( Drawing a free body diagram will help illustrate the situation).
gneill said:Perhaps there was an editing problem in the original text of the problem (is it from a textbook?). If the final sentence was truncated in error and was meant to read:
"Determine the friction force required to stop the ball from slipping."
then you might have a viable question if the coefficient of friction given was for static friction rather than kinetic friction.
Yes, that does sound like the right reading, but I still see a difficulty. To find the friction force we do not need the coefficient of friction. We can find the force from the other information, then find the minimum coefficient.gneill said:Perhaps there was an editing problem in the original text of the problem (is it from a textbook?). If the final sentence was truncated in error and was meant to read:
"Determine the friction force required to stop the ball from slipping."
then you might have a viable question if the coefficient of friction given was for static friction rather than kinetic friction.
True! I suspect that the kinetic friction coefficient that was listed may have been a value looked up in a reference and provided as a potentially relevant value. Perhaps @joelm can confirm/deny this if he returns to the thread.haruspex said:Yes, that does sound like the right reading, but I still see a difficulty. To find the friction force we do not need the coefficient of friction. We can find the force from the other information, then find the minimum coefficient.