p445hkk20001 發表於 11-9-2010 22:15 http://www4.nakuz.com/bbs/images/common/back.gif
慢..
呢個所謂既力其實 都只係 friction
因為車郁得慢左 我地仲係咁快
所以 佢要令我地唔可以係車表面上郁
所以要減我地速 令我地同車 保持相對靜止..
所以 當架車停定 完全停晒
我地仲係會有慣性向前
所以出現friction 減我地速
但係 呢個friction
唔會令我地有個後既速度
呢一點就係我唔明既地方... 我認為係
簡單講
車 減速 咁我地慣性改變為向後加速
所以車靜止時 我地慣性 都係想減速 我認為係
簡單講
車 減速 咁我地慣性改變為向後加速
所以車靜止時 我地慣性 都係想減速 ...
p445hkk20001 發表於 11-9-2010 22:36 http://www4.nakuz.com/bbs/images/common/back.gif
慣性是指物體的motion 吧= =
慣性不應該有force 啊= =
尤其呢種有d似左constant既force... 慣性有力架
你坐升降機 落樓果陣 你會輕左架 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...
bunbunbunbun 發表於 13-9-2010 02:22 http://www4.nakuz.com/bbs/images/common/back.gif
...
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.
my English is also poor
totally sorry about that 其實唔洗諗到咁深入
當車減速時,,左腳受力大,,於是身體就要將重心拉到右腳果一邊保維平衡
再之後,,,車停了,,,左腳和右腳受力一致,,,但因為你身體重心仲係右腳果一邊,,
所以車停左,右腳受力就大左,就會有呢一個感覺
諗得簡單D就OK 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)
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