A motion sensor at rest sends out 2 consecutive ultrasonic signal (or pulse) of speed 340ms-1 to towards a moving trolley, which is moving away from the sensor
The 1st signal is received before sending the 2nd signal is sent.
If the time lag between the sent and received 1st signal t1 = 0.01s,
If the time lag between the sent and received 2nd signal t2 = 0.0105s,
what's the average speed of the trolley in ms-1?
(講明先, 我做到個答案同書唔同)
[求救] [急問] 會考 Physics Mechanics!!
2008-03-23 10:59 pm
回答 (1)
2008-03-24 3:41 am
✔ 最佳答案
s=(340)(0.0105-0.01)/2..........除二因為來回的訊息!!~s=0.085m
所以the average speed of the trolley is 0.085/)0.0105-0.01)
答案=170m/s
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