how exactly does a train stay on track ? the wheels are like are made of metal and so is the track and i dont understand ! :/

Question

anonymous · Answer

You are probably thinking about friction here, and that the two metals are quite smooth, so how does it move forward.  Remember that the force of friction opposes motion (which gives the grip to move).  However the magnitude of this force is equal to the product of the coefficient of friction and the normal reaction to the surface i.e. $F=\mu R$.  But recall that $R=mg$ where the $m$ is mass, and $g$ the acceleration of gravity.  Trains are heavy, and so their normal reaction is large, and even if the coefficient of friction $\mu$ is small, the large mass gives enough of a grip to move along the tracks.

If you ever watch a train move of, you will see that the driving wheels will sometimes spin in place before they "catch" the track to move the train forward.

anonymous · Answer

here there is a very good explanation for it http://gumbo.blogspot.com/2009/07/how-trains-stay-on-track.html

anonymous · Answer

Explained by the master himself.  Thanks for that mridul. Just goes to show that I shouldn't read more into a question than what is actually being being asked. I just presumed Feynman gal meant friction.  Slap on the wrist for me.

anonymous · Answer

umm that was what i was searching for thanks  @mridul and johnny u re way of interpretting was interesting too so not a slap on ur wrist for u :P

anonymous · Answer

Now you tell me.  I am now putting my well used ruler away, and immersing my glowing pink wrists in some cold water ;)

anonymous · Answer

ha ha :P how sad !