請教物理高手! - Ans.fyi 參考答案

請教物理高手!

mingchak

2009-05-14 5:33 am

一男孩站在一幅大牆壁前有規律地擊掌，擊掌的頻率為3Hz‧他發現回音和擊掌聲是完全一致的‧求當他停止擊掌後，他聽到

(a)多一次回音和
(b)多三次回音時，
男承和牆的距離。
(聲音在空氣中的速率是330ms-1)

求解算和計算步驟!

回答 (1)

天同

2009-05-14 6:11 am

✔ 最佳答案

(a) Since period between successive hand clapping = 1/3 s
time for sound wave to trave from the boy to the wall and back = 1/3 s, so that he can hear the echo of his last hand-clap
hence distance of boy from the wall
= (330 x 1/3)/2 m = 55 m
(b) The echo from his first hand-clap arrives back to the boy 1/3 s after his third hand-clap, so that he can still hear 3 hand-claps after he has stopped clapping his hand.
Therefore, the echo takes 1 s to travel to the wall and back
hence distance = (330 x 1)/2 m = 165 m

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