A classical mechanics problem by Aleksander Lund
Alex is riding the train home from work. After a long day, he stares out of the window. It is raining straight towards the window from outside. And the rain is rolling straight down on the window until the train starts moving. As the train starts moving , he notices how the raindrops seems to decend from the top to the bottom of the at an angle backwards . As a physicist it doesn't take alex long to derive, that the mechanic behind this is simply the airresistance pushing the droplets in refference to his point of view. Now the train is about to arrive at its destination. It slows down as it moves toward the station. He now looks at the droplets again, as the train is just about to stop ~ approximately 2-3 seconds before it stops completely. What path do he see the dropplets taking at this point, from Alex's point of view?
All angles in refference to Alex's point of view, with foreward being the trains moving direction.
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1 solution
If you one day get to observe this yourself, you will see that the friction isn't strong enough if the acceleration of the braking is just about 1.2 m/s^2. Which is about every train. (If the train doesn't do this, then you should be worried, that there is something wrong with the brakes) =)