一辆汽车以36km/h的速度匀速行驶10s,然后又以1.5m/s2的加速度匀加速行驶10s.求:(1)汽车在20s内的位 一辆汽车,以36km/h的速度匀速行驶10s,然后以1m/s...
\uff0812\u5206\uff09\u6c7d\u8f66\u4ee536km/h\u7684\u901f\u5ea6\u5300\u901f\u884c\u9a7610s\uff0c\u7136\u540e\u53c8\u4ee51.5m/s 2 \u7684\u52a0\u901f\u5ea6\u5300\u52a0\u901f\u884c\u9a7610s\u3002\u6c42\uff1a\uff081\uff09\u6c7d\u8f66\u572815s\uff081\uff0917.5m/s (2)275m (3)13.75m/s \u8bd5\u9898\u5206\u6790\uff1a\uff081\uff09\u7531\u901f\u5ea6\u516c\u5f0f\uff1a \uff082\uff09\u6c7d\u8f66\u572820s\u5185\u7684\u4f4d\u79fb\uff1a \uff083\uff09\u4f9d\u5e73\u5747\u901f\u5ea6\u516c\u5f0f\uff1a \u70b9\u8bc4\uff1a\u672c\u9898\u8981\u6c42\u5b66\u751f\u719f\u7ec3\u638c\u63e1\u901f\u5ea6\u516c\u5f0f\u548c\u4f4d\u79fb\u516c\u5f0f\uff0c\u5e76\u80fd\u7075\u6d3b\u8fd0\u7528\u53bb\u89e3\u76f8\u5173\u95ee\u9898\u3002
\uff081\uff0936km/h=10m/s\uff0c\u6c7d\u8f66\u5300\u901f\u8fd0\u52a8\u7684\u4f4d\u79fbx1=vt1=10\u00d710m=100m\uff0c\u6c7d\u8f66\u5300\u52a0\u901f\u76f4\u7ebf\u8fd0\u52a8\u7684\u4f4d\u79fbx2\uff1dv0t2+12at22\uff1d10\u00d710+12\u00d71\u00d7100m=150m\u5219\u6c7d\u8f66\u5728\u8fd920s\u5185\u7684\u4f4d\u79fbx=x1+x2=100+150m=250m\uff0e\uff082\uff09\u6c7d\u8f66\u572820s\u5185\u7684\u5e73\u5747\u901f\u5ea6.v\uff1dxt\uff1d25020\uff1d12.5m/s\uff0e\u7b54\uff1a\uff081\uff09\u6c7d\u8f66\u5728\u8fd920s\u5185\u7684\u4f4d\u79fb\u662f250m\uff1b\uff082\uff09\u6c7d\u8f66\u5728\u8fd920s\u5185\u7684\u5e73\u5747\u901f\u5ea6\u662f12.5m/s\uff0e
汽车的初速度:v0=36km/h=10m/s(1)汽车在20s内的位移分为匀速运动位移和匀加速运动位移:
前10s内匀速运动的位移x1=v0t=10×10m=100m
后10s内做匀加速运动的位移:x2=v0t+
1 |
2 |
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故汽车在前20s内的总位移:x=x1+x2=100+175m=275m
(2)由题意知汽车运动前10s做匀速运动,故15s末是汽车做匀加速运动5s末的瞬时速度,根据速度时间关系有:
v1=v0+at=10+1.5×5m/s=17.5m/s
(3)根据平均速度公式,汽车在前20s内的平均速度:
. 绛旓細36km/h=10m/s 2s=v澹皌+v杞t 2s=4脳(340+10)s=2脳350 s=700m 鏁板杈呭鍥㈠洟鍛樹负鎮ㄨВ绛旓紝鏈夐敊璇鎸囨锛屼笉鏄庣櫧璇疯拷闂傛病闂灏遍噰绾冲惂锛岀湡蹇冨笇鏈涜兘瀵逛綘鐨勫涔犳垨鐢熸椿鏈夋墍甯姪锛 绛旓細36km/h=10m/s 璁 楦g瑳鏃惰窛绂诲北宕 L 340x4 + 10 x 4 =2L L=700m 鍙告満鍚埌鍥炲0鏃剁灞憋細L- 10 x 4= =66m 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; 绛旓細鈭存鏃姹借溅绂诲北宕栫殑璺濈涓(700-350/17)-(20-10/17)=680-340/17=660m 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... 绛旓細瑙o細姹借溅鐨勯熷害v1=36km/h=10m/s锛岃椹鹃┒鍛樻寜鍠囧彮鍚庯紝鍠囧彮澹颁紶鍒扮粷澹佽繑鍥炴苯杞︾敤鐨勬椂闂翠负t锛屽湪鏃堕棿t鍐咃紝姹借溅琛岄┒鐨勮窛绂伙細s1=v1t=10m/s脳t锛屽0闊充紶鎾殑璺濈锛歴2=v2t=340m/s脳t锛岃鎸夊枃鍙椂姹借溅鍒板北宕栫殑璺濈涓簊锛岀敱棰樼煡锛2s=s1+s2锛屽嵆锛2脳875m=10m/s脳t+340m/s脳t锛岃В寰楋細t=5s锛庣瓟... 绛旓細鎮ㄥソ锛36KM/H=10M/S锛屾墍浠姹借溅鐨勯熷害涓10M/S,鑰屽0闊冲湪绌烘皵涓殑浼犳挱閫熷害绾︿负340M/S锛4S鍐呮苯杞﹀墠杩涗簡40M锛屽0闊充紶鎾簡340X4=1360M锛岃鍚埌鍥炲0鏃惰窛灞卞礀Xm锛屽彲寰2X+40=1360锛岃В寰梄=660M 鐞冮噰绾硚 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 绛旓細鐢遍鎰忓彇鍒濋熷害鏂瑰悜涓烘鏂瑰悜锛屽垯v0=36km/h=10m/s锛屽姞閫熷害a=-5m/s2锛1锛夋牴鎹熷害鏃堕棿鍏崇郴姹借溅鍒硅溅鍚1s鐨勯熷害澶у皬涓簐1=v0+at=10+锛-5锛壝1m/s=5m/s锛2锛夋牴鎹熷害鏃堕棿鍏崇郴姹借溅鍒硅溅鍚庡仠姝㈣繍鍔ㄧ殑鏃堕棿t=0?v0a锛0?10?5s锛2s锛3锛夊洜涓4s澶т簬姹借溅鍋滆溅鏃堕棿锛屾晠4s鏈苯杞︾殑閫熷害涓0锛庣瓟锛氾紙1锛... 本站交流只代表网友个人观点,与本站立场无关 |