慣性is just a phenomenon, if you draw a force diagram of a lift accelerating downwards, there is no such thing as 慣性
The reason you feel yourself being pulled in the mtr is because of the tension within your body.
When the train accelerate/decelerate, the train exerts a force on your feet (friction) so that you move along with the train.
However, the friction only affects your feet but not your body, so muscles in your body will create a tension to keep your body moving with your feet.
When the train moves at a constant speed, your body still have tension, and will pull your body in the opposite direction.
Therefore, you feel jerk on your other foot.
Theoretically, you also feel this when the mtr accelerate, but since the jerk(rate of change of acceleration) is smaller than when the train decelerate, the feeling is not as significant.
you can understand this easier if you get yourself a block of jelly and move it around
慣性is just a phenomenon, if you draw a force diagram of a lift accelerating downwards, there is no ...
[H]bunbunbunbun 發表於 13-9-2010 02:22
...
i am sorry about that...
but ...
i can't find my answer in your post...
i am not a intelligent or gifted student
so...
may you explain it in a simple way ..?
sorry that...
but now..
when the train is decelerating
i would feel that i am being pushed
it is easily to get
but when the train completely stop
i was being pulled but actually my body is still moving forward ....
would the friction affect myself in this way?
it is strange.
when it is decelerating, your body would strike a balance
you may not sense when the train would stop, the force which balances your body probably is still acting..
when it stoped, the force of your left/right legs may not be the same....there's a net force
um..im just answering this question externally and unphysically@@
Great observation leads great study(Y)
發表於 11-9-2010 22:36:40