一辆汽车以36km/h的速度匀速驶向前面的山崖,司机鸣笛后 4s听到了回声,求听到回声时距山崖的距离.
\u4e00\u8f86\u6c7d\u8f66\u4ee536km/h\u7684\u901f\u5ea6\u5300\u901f\u5411\u524d\u9762\u7684\u5c71\u5d16\uff0c\u53f8\u673a\u9e23\u7b1b\u540e4S\u542c\u5230\u4e86\u56de\u58f0\uff0c\u6c42\uff1a\u542c\u5230\u56de\u58f0\u65f6\u6c7d\u8f66\u5c45\u5c71\u5d16\u7684\u8ddd\u79bb\uff1fv=36km/h=10m/s
4\u79d2\u5185\uff0c\u58f0\u97f3\u4f20\u64ad\u7684\u8ddd\u79bb S\u58f0=v\u58f0t=340m/s\u00d74s=1360m
4\u79d2\u5185\uff0c\u8f66\u8d70\u7684\u8ddd\u79bb S\u8f66=v\u8f66t=10m/s\u00d74s=40m
\u56e0\u6b64\uff0c\u542c\u5230\u56de\u58f0\u65f6\uff0c\u8f66\u5230\u5c71\u5d16\u7684\u8ddd\u79bb S=\uff08S\u58f0-S\u8f66\uff09/2=\uff081360m-40m\uff09/2=660m
\u89e3\uff0c36KM/h=10M/s\u56db\u79d2\u540e\u9a91\u8f66\u884c\u9a76\u4e864*10=40M
\u2235\u58f0\u97f3\u5728\u7a7a\u6c14\u4e2d\u4f20\u64ad\u901f\u5ea6\u4e3a340M/S
\u22344\u79d2\u58f0\u97f3\u4f20\u64ad\u4e86340X4=1360m
\u8bbe\u542c\u5230\u56de\u58f0\u65f6\u8ddd\u79bb\u5c71\u5d16\u7684\u8ddd\u79bb\u4e3ax\uff0c\u6c7d\u8f66\u9e23\u7b1b\u65f6\u8ddd\u79bb\u4e3aY\uff0c\u6839\u636e\u4ee5\u4e0a\u6761\u4ef6\u90a3\u4e48\u6211\u4eec\u53ef\u4ee5\u5efa\u7acb\u65b9\u7a0b\uff1a
X+y=1340
y-x=40
\u89e3\u8fd9\u4e2a\u4e8c\u5143\u4e00\u6b21\u65b9\u7a0b\u7684x=650, y=690
\u7b54\uff1a\u6c7d\u8f66\u9e23\u7b1b\u65f6\u8ddd\u79bb\u5c71\u5d16690m\uff0c\u542c\u5230\u56de\u58f0\u8ddd\u79bb\u5c71\u5d16650m
\u5e0c\u671b\u53ef\u4ee5\u5e2e\u5230\u4f60\uff0c\u671b\u91c7\u7eb3\u3002
球采纳~
v车=36km/h=10m/s
S声-S车=2L
v声t-v车t=2L
340 x 4-10 x 4=2L
L=660(m)
听到回声时距山崖660米
绛旓細鍥炵瓟锛氳В:姹借溅鐨勯熷害v1=36km/h=36脳13.6m/s=10m/s, 璁鹃┚椹跺憳鎸夊枃鍙悗,鍠囧彮澹颁紶鍒扮粷澹佽繑鍥炴苯杞︾敤鐨勬椂闂翠负t, 鍦ㄦ椂闂磘鍐,姹借溅琛岄┒鐨勮窛绂: s1=v1t=10m/s脳t, 澹伴煶浼犳挱鐨勮窛绂: s2=v2t=340m/s脳t, 璁炬寜鍠囧彮鏃舵苯杞﹀埌灞卞礀鐨勮窛绂讳负s, 鐢遍鐭,2s=s1+s2, 鍗:2脳875m=10m/s脳t+340m/s...
绛旓細36km/h=10m/s s1=(10+340)脳2/2=350m s2=10脳2=20m s=s1-s2=330m 鎵姹傝窛绂绘槸330m
绛旓細锛1锛夊仛鍔熶负W=P*t=60KW*10min=60KW*600s=3.6脳10^7J锛涳紙2锛夌敱浜嶱=F*V锛屽叾涓璓鐨勫崟浣嶄负w锛孷鐨勫崟浣嶄负m/s锛60KW=60000w锛 36KM/h=10m/s锛孎=P/V=(60000w锛/锛10m/s锛=6000N;
绛旓細锛姹借溅鐨勯熷害v=36km/h=10m/s4绉掗挓鍐呮苯杞﹁蛋鐨勮矾绋媠1=4*10=40m,澹伴煶璧扮殑璺▼s2=4*340=1360m鎵浠姹借溅姹借溅楦g瑳鏄窛绂诲北宕栫殑璺濈s3=(s1+s2)/2=700m鎵浠ユ苯杞﹀惉鍒板洖澹版椂璺濈灞卞礀鐨勮窛绂籹=s3-s1=660m
绛旓細锛1锛姹借溅琛岄┒鐨勯熷害涓簐=36km/h=10m/s锛 鐢卞浘鍙煡锛屽徃鏈哄惉鍒板洖澹版椂璺濈灞卞礀涓篠 BC 锛屾牴鎹鎰忕敱v= s t 寰楋紝10m/s脳4s+S BC = 340m/s脳4s+10m/s脳4s 2 锛岃В寰桽 BC =660m锛庯紙2锛夌敱鍥惧彲鐭ワ紝姹借溅楦g瑳鏃剁灞卞礀鐨勮窛绂讳负AC锛屽嵆AB+BC锛岀敱v= s t 寰楋紝...
绛旓細姹借溅鐨勫垵閫熷害锛歷0=36km/h=10m/s锛1锛夋苯杞﹀湪20s鍐呯殑浣嶇Щ鍒嗕负鍖閫熻繍鍔ㄤ綅绉诲拰鍖鍔犻熻繍鍔ㄤ綅绉伙細鍓10s鍐呭寑閫熻繍鍔ㄧ殑浣嶇Щx1=v0t=10脳10m=100m鍚10s鍐呭仛鍖鍔犻熻繍鍔ㄧ殑浣嶇Щ锛歺2锛漹0t+12at2锛10脳10+12脳1.5脳102m=175m鏁呮苯杞﹀湪鍓20s鍐呯殑鎬讳綅绉伙細x=x1+x2=100+175m=275m锛2锛夌敱棰樻剰鐭ユ苯杞...
绛旓細=36km/h=10m/s锛宼 1 =10s锛宎=1m/s 2 锛宼 2 =10s锛1锛夊墠10s鍋氬寑閫熻繍鍔ㄧ殑浣嶇Щ涓猴細x 1 =v 0 t 1 =10脳10m=100m鍚10s涓庡姞閫熻繍鍔ㄧ殑浣嶇Щ涓猴細x 2 =v 0 t 2 + 1 2 a t 2 2 = 10脳10+ 1 2 脳1脳1 0 2 m =150m鎵浠姹借溅鍦ㄨ繖20s鍐呯殑浣...
绛旓細瑙o細v杞︼紳36km/h锛10m/s S杞+S澹帮紳2L v杞+v澹皌=2L 10m/s x t+340m/s x t = 2 x 700m t=4s 楦g瑳鍚4绉掑惉鍒板洖澹帮紝姝ゆ椂姹借溅涓庡北宕栫殑璺濈锛歋锛滾-S杞︼紳L-v杞锛700m-10m/s x 4s=660m
绛旓細36km/h=10m/s锛岃楦g瑳鏃姹借溅璺濋殰纰嶇墿x锛屽垯涓ょ鍚庤窛闅滅鐗﹛-20锛岃繖涓ょ澹伴煶鍏辫蛋浜唜+(x-20)=2x-20銆傚垯2x-20=V澹*t锛屽嵆2x-20=340*2锛岃В寰梮=350m 鍗抽福绗涙椂姹借溅璺濋殰纰嶇墿350m
绛旓細姹借溅琛岄┒鐨勯熷害锛歷1=36km/h=10m/s锛岀敱v=st鍙緱锛屽湪t=4s鐨勬椂闂村唴锛屾苯杞﹁椹剁殑璺濈锛歴1=v1t=10m/s脳4s=40m锛屽0闊充紶鎾殑璺濈锛歴2=v2t=340m/s脳4s=1360m锛岃楦g瑳鏃舵苯杞﹀埌灞卞礀鐨勮窛绂讳负s锛屽垯锛2s=s1+s2锛屸埓s=12锛坰1+s2锛12脳锛40m+1360m锛=700m锛庣瓟锛氭苯杞﹂福绗涘璺熷ぇ灞变箣闂寸殑璺濈鏈700...