if a car is travelling at say 40miles an hour how fast is the bottom of the wheel travelling in relation to the ground? with the wheel spinning, it seems to me that the bottom bit is travelling backwards and therefore cancells out the forward motion of the car... hmmm...
2006-10-03 09:21:28 · 27 answers · asked by wildmanski 2 in Entertainment & Music ➔ Jokes & Riddles
Every part of the wheel is moving forwards* but at different speeds at different times - faster at the top and slower at the bottom. As each part is sometimes at the top and sometimes at the bottom, you can see that each part is constantly speeding up and slowing down, as the wheel spins. (This is all relative to the road of course, which is what you asked).
*The one exception: a point on the EXTREME outside of the wheel stops for an instant while it touches the road.
If a point is even a millionth of an inch from the outside of the wheel, it never quite becomes stationary.
The amount by which it speeds up and slows down depends on how far it is from the edge: if it's right on the hub, it doesn't at all - it goes at the same speed as the car all the time.
No part of the wheel ever goes backwards relative to the road, though it does relative to the car.
Think about it carefully: it'll make sense!
2006-10-03 13:45:30 · answer #1 · answered by Anonymous · 0⤊ 1⤋
Loufedalis has got it spot-on, unlike many people who have handed over non-commital answers to score an easy 2 points.
The wheels on the car can rotate around 360 in total - and can travel either forward or back. Their motion is directly linked to the car's motion - allowing the car to move either backward or forward, including turns. In your hypothetial situation, the car is travelling at 40 miles per hour - the wheels will be travelling at the same speed in relation to the ground in order to maintain the speed that the car is travelling at.
2006-10-03 10:48:05 · answer #2 · answered by squirrellondon 4 · 0⤊ 0⤋
Because the wheel is 360 degrees, the wheel can travel only in two directions, forward or backward. It the car is moving at 40MPH forward, then the wheel, being attached to the car has no other choice than to travel with the car at the same speed.
2006-10-03 09:57:59 · answer #3 · answered by loufedalis 7 · 1⤊ 0⤋
Actually, the bottom of the tire, that is in contact with the road surface, is moving backwards at the same speed as the car is moving forward and is therefore actually not moving at all. It's standing still. But at the top, it's travelling twice as fast as the car.
2006-10-03 09:28:38 · answer #4 · answered by vmmhg 4 · 2⤊ 0⤋
You have to take the entire tire into account. What appears to be backward motion is only the second half of the complete rotation. Since the bottom of the tire is not independent from the top there is always a part that will appear to be moving counter to the forward motion.
2006-10-03 10:35:26 · answer #5 · answered by al p 3 · 1⤊ 0⤋
unless the wheels are spinning at the exact bottom point the wheel is not travelling forward, merely holding the ground in one spot. At the top however the wheel is travelling inversley propotionate to the bottom so would be travelling twice as fast to keep up i ithink. this is how i see it in my minds eye anyway. Hope my ideas help.
2006-10-03 09:26:52 · answer #6 · answered by rob e 2 · 1⤊ 0⤋
The bit of wheel in contact with the ground has to be stationary because otherwise it would blow my mind !!! It looks like it is going backwards because the rest of the wheel is spinning and the point of contact should appear stationary....Iknow what I mean anyway.... A bit like explaining doplar....
2006-10-03 10:32:16 · answer #7 · answered by perisamablue 2 · 0⤊ 0⤋
The bottom of the wheel is always going to be directly below the axle which is attached to the car. If the car is going at 40mph then so is the bottom of the tyre.
2006-10-03 10:41:32 · answer #8 · answered by saljegi 3 · 1⤊ 0⤋
Right, the base of the wheel is motionless otherwise it would skate over the top of the ground. The loss of traction would be the only time where the two speeds vary.
Nice question, I enjoyed that!
2006-10-03 21:21:13 · answer #9 · answered by Captain Eyewash 5 · 0⤊ 0⤋
yeah well what about the velocity at the back edge where it is travelling upward against gravity (9.8m/s2) and at the front edge 9.8m/s2 down while, The force diffence between the front edge and the back edge is 3 G's that's enough force to make you throw up X4 tires = 12 G's that would kill you. Man I never want to drive again now.....
thanks alot for freaking me out.
2006-10-03 11:27:48 · answer #10 · answered by Anonymous · 0⤊ 0⤋