Mechanics 緊急，thx for answer ! (20 marks)
2007-03-30 7:16 am
The timer-scaler will record the time elapsed during which the light from the lamp is cut off by the card on the trolley. It records 40 ms and 20 ms as the 4.0 cm card on the trolley passes the upper and lower phototransistor stations respectively. The time taken by the trolley to travel from the upper to the lower station is 2.0 second. What is the change in the velocity and acceleration of the troolley when it moves between these two phototransistors?
回答 (2)
2007-03-30 8:10 am
✔ 最佳答案
Explaination of the question:the 4cm card on the trolley spend 40ms(1ms=1/1000s) to pass the upper phototransistor station first
after 2s, it arrive the lower phototransistor station, it spend 20ms to pass the lower phototransistor station
Answer:
velocity of the trolley when it pass the upper phototransistor station, u1=d/t1
=4cm/40ms
=0.04m/0.04s
=1ms-1
velocity of the trolley when it pass the lower phototransistor stations, u2=d/t2
=4cm/20ms
=0.04m/0.02s
=2ms-1
so Change in velocity = u2-u1=2-1=1ms-1
Acceleration = (v-u)/t=(u2-u1)/t
=(2-1)/2
=0.5 m s-2
is it detail enough to understand?
2007-03-30 8:52 am
條問題話有架車仔上面有張卡紙4cm 長，由鈄台上溜下來，會遮兩次電眼，第一次為時40ms ，第二次為時20ms ，而車子要2秒由上面電眼到下面電眼。
而解答上面答左。
而解答上面答左。
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