Goosemaster
Lifer
- Apr 10, 2001
- 48,775
- 3
- 81
Originally posted by: TuxDave
I honestly have a hunch that if there is guaranteed no slipping, then it stays put. Anyone want to back me up?
Originally posted by: soniikboom
What if instead of just simply pulling the string...a man holding the string pulled it up to his chest. How would this affect the movement? I think this was actually the question I got.
Originally posted by: Indolent
Originally posted by: TuxDave
I honestly have a hunch that if there is guaranteed no slipping, then it stays put. Anyone want to back me up?
Nope, because it can roll.
Originally posted by: Indolent
Originally posted by: dighn
Originally posted by: HardcoreRobot
when you tug on it, it exerts an equal and opposite force against the bike rim. (so, a vector heading to the left). this vector gets decomposed to the horz and vert components. we dont care about the horz, just the vert, which is pushing it down. this causes the wheel to move counter clockwise and roll the bike forward.
i have no idea if that is right, but i tried to make it sound convincing
but no slipping means there's a counter force at the bottom of the wheel, so it should turn clockwise and move backward
Correct, it will move backwards. The center of rotation is the point of contact between the wheel and the ground. Since the force is higher, it will move it backwards. No slip conditions is the key.
Originally posted by: Kev
Originally posted by: Indolent
Originally posted by: dighn
Originally posted by: HardcoreRobot
when you tug on it, it exerts an equal and opposite force against the bike rim. (so, a vector heading to the left). this vector gets decomposed to the horz and vert components. we dont care about the horz, just the vert, which is pushing it down. this causes the wheel to move counter clockwise and roll the bike forward.
i have no idea if that is right, but i tried to make it sound convincing
but no slipping means there's a counter force at the bottom of the wheel, so it should turn clockwise and move backward
Correct, it will move backwards. The center of rotation is the point of contact between the wheel and the ground. Since the force is higher, it will move it backwards. No slip conditions is the key.
if there was slipping then the bike would move backwards because there would be no force of friction to move the boke forward.
Originally posted by: Pantoot
Originally posted by: TuxDave
I honestly have a hunch that if there is guaranteed no slipping, then it stays put. Anyone want to back me up?
If there was slipping then the bike would stay put. The hub would be stationary and the wheel would be able to spin freely (as it slipped across the ground.) Since we are told that there is no slipping, when the point on the far end of the wheel moves toward the puller, the bike must move away as the wheel turns.
not true, becuase the force is not purely rotational. imagine if the string was at the 180 degree position (halfway up on the left). there would be NO rotational force there, only a force to pull the entire wheel to the right. which, with slippage, would drag the wheel without spinning. the bike would still move. even though the string is not in this position, a component of its force acts like this.Originally posted by: Pantoot
Originally posted by: TuxDave
I honestly have a hunch that if there is guaranteed no slipping, then it stays put. Anyone want to back me up?
If there was slipping then the bike would stay put. The hub would be stationary and the wheel would be able to spin freely (as it slipped across the ground.) Since we are told that there is no slipping, when the point on the far end of the wheel moves toward the puller, the bike must move away as the wheel turns.
Originally posted by: Yossarian
force P isn't important, the moment exerted about the axle by force P is what matters. resolve force P into components parallel and perpendicular to the wheel at the point of contact. the parallel component goes down and to the right, exerting a clockwise moment. the bike goes forward.
Originally posted by: Darthvoy
I think they are trying to see your analytical skills. I would answer something to the effect that it is impossible to know how the bike will move if we don't know the strength of the string. I was asked question like that in my old job because they wanted to see how my problem solving skills were.
Originally posted by: Kev
I just did a mini experiment with a bottle cap (haha) and I see what indolent is talking about
Originally posted by: TuxDave
I don't think there's been an official answer on that board either... it looks like they're debating it too.