如图所示是某建筑工地用升降机提升大理石的滑轮组示意图.滑轮组通过固定架被固定住,滑轮组中的两个定滑
\u67d0\u5efa\u7b51\u5de5\u5730\u7528\u5347\u964d\u673a\u63d0\u5347\u5927\u7406\u77f3\u7684\u793a\u610f\u56fe\u5982\u56fe\u6240\u793a\u3002\u5347\u964d\u673a\u8d27\u7bb1\u7684\u91cd\u529b\u662f400N\uff0cg\u53d610N/kg\u3002\u4e0d\u8ba1\u6ed1\u8f6e\u548c\u94a2\u4e1d\u7ef3(1) (2) \uff083\uff09 (1) \u6bcf\u5757\u5927\u7406\u77f3\u91cd\uff1a \uff082\u5206\uff09(2) \u5347\u964d\u673a\u4e00\u6b21\u80fd\u63d0\u8d77\u7684\u5927\u7406\u77f3\u5757\u6570\uff1a \uff081\u5206\uff09(3) \u94a2\u4e1d\u7ef3\u7aef\u79fb\u52a8\u7684\u8ddd\u79bb\uff1a \uff081\u5206\uff09 \u628a\u8d27\u7269\u63d0\u534715 m\u505a\u7684\u529f\uff1a \uff081\u5206\uff09\u5347\u964d\u673a\u7684\u529f\u7387\uff1a \uff081\u5206\uff09\uff081\uff09\u5148\u7531m=\u03c1V\u8ba1\u7b97\u6bcf\u5757\u5927\u7406\u77f3\u7684\u8d28\u91cf\uff0c\u518d\u7531G=mg\u6c42\u51fa\u6bcf\u5757\u5927\u7406\u77f3\u7684\u91cd\u529b\uff1b\uff082\uff09\u7531\u56fe\u53ef\u77e5\u6709\u4e09\u6bb5\u94a2\u4e1d\u63d0\u7740\u8d27\u7bb1\uff0c\u5219\u8d27\u7bb1\u603b\u91cd\u662f\u94a2\u4e1d\u62c9\u529b\u76843\u500d\uff0c\u53bb\u6389\u8d27\u7bb1\u7684\u91cd\u529b\u5c31\u662f\u7816\u7684\u91cd\u529b\uff0c\u4e5f\u5c31\u80fd\u6c42\u51fa\u7816\u7684\u5757\u6570\uff1b\uff083\uff09\u94a2\u4e1d\u7ef3\u79fb\u52a8\u7684\u8ddd\u79bb\u662f\u8d27\u7bb1\u4e0a\u5347\u8ddd\u79bb\u76843\u500d\uff0c\u5229\u7528W=Fs\u6c42\u51fa\u94a2\u4e1d\u7ef3\u505a\u7684\u529f\uff0c\u518d\u5229\u7528 \u5f97\u94a2\u4e1d\u7ef3\u7684\u62c9\u529b\u7684\u529f\u7387\uff0e\u8be5\u9898\u6d89\u53ca\u5230\u5bc6\u5ea6\u3001\u91cd\u529b\u3001\u529f\u3001\u529f\u7387\u3001\u6ed1\u8f6e\u7ec4\u7b49\u7684\u8ba1\u7b97\uff0c\u662f\u4e00\u7efc\u5408\u6027\u8f83\u5f3a\u7684\u9898\uff0c\u5728\u8ba1\u7b97\u8fc7\u7a0b\u4e2d\u8981\u6ce8\u610f\u5404\u4e2a\u7269\u7406\u91cf\u4e4b\u95f4\u7684\u5173\u7cfb\uff0c\u8003\u67e5\u4e86\u5b66\u751f\u7684\u7efc\u5408\u5e94\u7528\u80fd\u529b\uff0c\u5c5e\u4e8e\u96be\u9898\uff0e\u3010\u8003\u70b9\u3011\u5bc6\u5ea6\u516c\u5f0f\u7684\u5e94\u7528\uff1b\u6ed1\u8f6e\u7ec4\u7ef3\u5b50\u62c9\u529b\u7684\u8ba1\u7b97\uff1b\u91cd\u529b\u7684\u8ba1\u7b97\uff1b\u529f\u7387\u7684\u8ba1\u7b97\uff0e
\uff081\uff09\u7531\u56fe\u793a\u53ef\u77e5\uff0c\u6ed1\u8f6e\u7ec4\u627f\u91cd\u7ef3\u5b50\u7684\u80a1\u6570n=3\uff0c\u5347\u964d\u673a\u4e00\u6b21\u80fd\u591f\u63d0\u8d77\u7684\u603b\u91cd\uff1aG\u603b=nF\u6700\u5927=3\u00d72000N=6000N\uff0c\u5347\u964d\u673a\u4e00\u6b21\u80fd\u63d0\u8d77\u7684\u5927\u7406\u77f3\u7684\u603b\u91cd\uff1aG\u77f3=G\u603b-G0=6000N-400N=5600N\uff1b\uff082\uff09\u94a2\u4e1d\u7ef3\u7aef\u79fb\u52a8\u7684\u8ddd\u79bb\uff1as=nh=3\u00d715m=45m\u628a\u8d27\u7269\u63d0\u534715m\u62c9\u529b\u505a\u7684\u529f\uff1aW=Fs=2000N\u00d745m=9\u00d7104J\u5347\u964d\u673a\u7684\u529f\u7387\u4e3aP=Wt=9\u00d7104J60s=1500W\uff0e\u7b54\uff1a\uff081\uff09\u8be5\u5347\u964d\u673a\u4e00\u6b21\u6700\u591a\u80fd\u5300\u901f\u63d0\u53475600N\u7684\u5927\u7406\u77f3\uff1b\uff083\uff09\u5347\u964d\u673a\u7684\u529f\u7387\u4e3a1500W\uff0e
(1)由ρ=
m |
V |
m=ρV=2.8×103kg/m3×1.0×10-2m3=28kg
每块大理石重:G=mg=28kg×10N/kg=280N;
升降机一次能够提起的总重为G总=3×F最大=3×2000N=6000N
升降机一次能提起的大理石的总重为G石=G总-G0=6000N-300N=5700N
升降机一次能提起的大理石的块数为n=
G石 |
G |
5700N |
280N |
(2)提升15块大理石的过程中,钢丝绳端移动的距离:s=3h=3×15m=45m
F=
1 |
3 |
1 |
3 |
(3)把货物提升15m拉力做的功:W=Fs=1500N×45m=6.75×104J
升降机的功率为P=
W |
t |
6.75×104J |
60s |
(4)W有用=Gh=15×280N×15m=6.3×104J,
η=
W有用 |
W总 |
6.3×104J |
6.75×104J |
故选C.
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绛旓細鍔熺巼P=鍔焀/鍋氬姛鏃堕棿s銆傚姛W=鍋氬姛鐨勫姏F脳鍋氬姛鐨勮窛绂籐 1.2t=12000kg 鎵浠ュ姏F=12000kg脳9.8N/kg=117600N路m銆2妤煎埌5妤硷紝姣忓眰3绫筹紝涓鍏变笂鍗囦簡9绫炽俉=F脳L=117600脳锛5-2锛壝3=1058400J锛堢劍灏旓級鎵浠=W/S=1058400梅10=105840W鐡=105.84kW锛堝崈鐡︼級鍗囬檷鏈鍔熺巼鏄105.84kW锛堝崈鐡︼級搴旇鏄...
绛旓細鍗囬檷鏈鎬婚噸锛欸=mg锛1.2脳1000kg脳10N/kg锛12000N 鍋氬姛锛歐锛滸h锛12000N脳锛3脳3m锛夛紳108000J 鍔熺巼锛歅锛漌/t锛108000J/10s锛10800W 鍗筹細10.8kW銆
绛旓細鍗囬檷鏈鐨勭浣撹繛鍚岃揣鐗╃殑鎬婚噸鍔涳細G=mg=1.2脳103kg脳10N/kg=1.2脳104N锛庝粠妤肩殑2灞備笂鍗囧埌5灞傜殑楂樺害涓猴細h=3m脳3=9m锛屽垯鍗囬檷鏈鸿嚦灏戝仛鐨勫姛涓篧=Gh=1.2脳104N脳9m=1.08脳105J锛涘崌闄嶆満鐨勫姛鐜囪嚦灏戜负锛歅=Wt=1.08脳105J10s=1.08脳104W锛庢晠閫夛細B锛
绛旓細W=F2s=2000N脳24m=48000J锛岄挗涓濈怀鑷敱绔媺鍔涚殑鍔熺巼锛歅=Wt=48000J30s=1600W锛涳紙3锛夋湁鐢ㄥ姛锛歐鏈=Gh=6000N脳6m=36000J锛屾诲姛锛歐鎬=P杈撳叆t=2000W脳30s=60000J锛岃瑁呯疆鐨勬晥鐜囷細畏=W鏈塛鎬幻100%=36000J60000J脳100%=60%锛庣瓟锛氾紙1锛夊湪鍖閫熸彁鍗囦腑锛岃揣鐗╁璐у帰搴曢儴鐨勫帇寮烘槸3000Pa锛涳紙...
绛旓細鍥炬槸鎻愬崌璐х墿鐨勬煇鍗囬檷鏈虹ず鎰忓浘銆傝揣鍘㈠唴鎵瑁呰揣鐗╃殑閲嶅姏鏄6000N,璐у帰鐨勯噸鍔涙槸2000N銆傝嫢涓嶈閽笣缁冲拰鍔ㄦ粦杞殑閲嶅姏,涓嶈鎽╂摝(1)鍦ㄥ寑閫熸彁鍗囦腑,婊戣疆缁勭殑鏈烘鏁堢巼鏄灏?2)鑻ュ崌闄嶆満鍦... 鍥炬槸鎻愬崌璐х墿鐨鏌愬崌闄嶆満绀烘剰鍥俱傝揣鍘㈠唴鎵瑁呰揣鐗╃殑閲嶅姏鏄6000 N,璐у帰鐨勯噸鍔涙槸2000 N銆傝嫢涓嶈閽笣缁冲拰鍔ㄦ粦杞殑閲嶅姏,涓嶈...
绛旓細F=(G1+G2)/4=锛6000+2000锛/4=2000N P=W/t=Fs/t=2000*6*4/30=1600w
绛旓細鈶0-2s鏄寑鍔犻熼樁娈碉紝鍔犻熷害a=5/2(m/s²)2-5s涓哄寑閫熼樁娈碉紝閫熷害v=5(m/s)5-8s涓哄寑鍑忛熼樁娈碉紝鍔犻熷害a'=-5/3(m/s²)鈶:a'=5/2:5/3=3:2
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