3 ms·
I can say with confidence that you're wrong about a point on a non-skidding wheel moving backwards. I can't read your book though, it says that the page is unav
by tgb 10y ago
I can say with confidence that you're wrong about a point on a non-skidding wheel moving backwards. I can't read your book though, it says that the page is unavailable.
Consider the wheel in the frame of the train. The train moves at velocity v relative to the ground. So the bottom of the wheel moves with velocity v backwards in the frame of the train. The top moves velocity v forward in that frame. All other points move at the same speed but in directions that aren't perfectly horizontal so move at a slower horizontal speed. But for a point to move backwards relative to the ground it must move at a horizontal speed greater than v in the frame of the train. So there is no such point.
- lotyrin 10y agoI haven't read this either, but the flange(?) of the wheel, the part below/behind the rail, is on the same lever as the point where the wheel contacts the rail (v), but further from the axis, so it's moving further (>v), also opposite the direction of the train's forward motion, so total negative speed, in the frame of the rail/ground. This is why a train is picked over most vehicles, which operate as you describe.
- tgb 10y agoYes, you're totally right, my analysis applies to bikes not trains! A tale in over-confidence / Google book previews availability.