ÌâÄ¿ÄÚÈÝ
7£®ÈçͼËùʾ£¬Á½¸ö°ëÔ²ÖùA¡¢B½ô¿¿×ž²ÖÃÓÚˮƽµØÃæÉÏ£¬ÆäÉÏÓÐÒ»¹â»¬Ô²ÖùC£¬ÈýÕ߰뾶¾ùΪR£®CµÄÖÊÁ¿Îªm£¬A¡¢BµÄÖÊÁ¿¶¼Îª$\frac{m}{2}$£¬ÓëµØÃæµÄ¶¯Ä¦²ÁÒòÊý¾ùΪ¦Ì£®ÏÖÓÃˮƽÏòÓÒµÄÁ¦ÀA£¬Ê¹A»ºÂýÒƶ¯£¬Ö±ÖÁCÇ¡ºÃ½µµ½µØÃ森Õû¸ö¹ý³ÌÖÐB±£³Ö¾²Ö¹£®Éè×î´ó¾²Ä¦²ÁÁ¦µÈÓÚ»¬¶¯Ä¦²ÁÁ¦£¬ÖØÁ¦¼ÓËÙ¶ÈΪg£®Ç󣺣¨1£©Î´ÀAʱ£¬CÊܵ½B×÷ÓÃÁ¦µÄ´óСF£»
£¨2£©¶¯Ä¦²ÁÒòÊýµÄ×îСֵ¦Ìmin£»
£¨3£©AÒƶ¯µÄÕû¸ö¹ý³ÌÖУ¬ÀÁ¦×öµÄ¹¦W£®
·ÖÎö £¨1£©¸ù¾Ý¹²µãÁ¦µÄƽºâÌõ¼þÇó½âCÊܵ½B×÷ÓÃÁ¦µÄ´óСF£»
£¨2£©Ïȸù¾Ý¹²µãÁ¦Æ½ºâÌõ¼þÇó½âBÊܵ½Cˮƽ·½Ïò×î´óѹÁ¦£¬ÔÙÇó³öB¶ÔµØÃæµÄѹÁ¦£¬¸ù¾ÝĦ²ÁÁ¦µÄ¼ÆË㹫ʽÇó½â£»
£¨3£©¸ù¾Ý¶¯Äܶ¨ÀíÇó½âAÒƶ¯µÄÕû¸ö¹ý³ÌÖУ¬ÀÁ¦×öµÄ¹¦W£®
½â´ð ½â£º£¨1£©CÊÜÁ¦Æ½ºâ£¬ÈçͼËùʾ£º
¸ù¾ÝƽºâÌõ¼þ¿ÉµÃ£º2Fcos30¡ã=mg£¬
½âµÃCÊܵ½B×÷ÓÃÁ¦µÄ´óСΪ£ºF=$\frac{\sqrt{3}}{3}mg$£»
£¨2£©CÇ¡ºÃ½µÂäµ½µØÃæʱ£¬B¶ÔCÖ§³ÖÁ¦×î´óΪFm£¬ÈçͼËùʾ£¬
Ôò¸ù¾ÝÁ¦µÄƽºâ¿ÉµÃ£º2Fmcos60¡ã=mg£¬
½âµÃ£ºFm=mg£»
ËùÒÔ×î´ó¾²Ä¦²ÁÁ¦ÖÁÉÙΪ£ºfm=Fmcos30¡ã=$\frac{\sqrt{3}}{2}mg$£¬
B¶ÔµÄµØÃæµÄѹÁ¦Îª£ºFN=mBg+$\frac{1}{2}{m}_{C}g$=mg£¬
BÊܵØÃæµÄĦ²ÁÁ¦Îª£ºf=¦Ìmg£¬
¸ù¾ÝÌâÒâÓУºfm=f£¬
½âµÃ£º¦Ì=$\frac{\sqrt{3}}{2}$£¬
ËùÒÔ¶¯Ä¦²ÁÒòÊýµÄ×îСֵΪ£º¦Ìmin=$\frac{\sqrt{3}}{2}$£»
£¨3£©CϽµµÄ¸ß¶ÈΪ£ºh=$£¨\sqrt{3}-1£©R$£¬
AµÄλÒÆΪ£ºx=$2£¨\sqrt{3}-1£©R$£¬
Ħ²ÁÁ¦×ö¹¦µÄ´óСΪ£ºWf=fx=2$£¨\sqrt{3}-1£©¦ÌmgR$£¬
¸ù¾Ý¶¯Äܶ¨ÀíÓУºW-Wf+mgh=0£¬
½âµÃ£ºW=$£¨2¦Ì-1£©£¨\sqrt{3}-1£©mgR$£®
´ð£º£¨1£©Î´ÀAʱ£¬CÊܵ½B×÷ÓÃÁ¦µÄ´óСΪ$\frac{\sqrt{3}}{3}mg$£»
£¨2£©¶¯Ä¦²ÁÒòÊýµÄ×îСֵΪ$\frac{\sqrt{3}}{2}$£»
£¨3£©AÒƶ¯µÄÕû¸ö¹ý³ÌÖУ¬ÀÁ¦×öµÄ¹¦WΪ$£¨2¦Ì-1£©£¨\sqrt{3}-1£©mgR$£®
µãÆÀ ±¾ÌâÖ÷ÒªÊÇ¿¼²éÁ˹²µãÁ¦µÄƽºâºÍ¶¯Äܶ¨Àí£¬½â´ð´ËÀàÎÊÌâµÄÒ»°ã²½ÖèÊÇ£ºÈ·¶¨Ñо¿¶ÔÏó¡¢½øÐÐÊÜÁ¦·ÖÎö¡¢ÀûÓÃƽÐÐËıßÐη¨Ôò½øÐÐÁ¦µÄºÏ³É»òÕßÊÇÕý½»·Ö½â·¨½øÐÐÁ¦µÄ·Ö½â£¬È»ºóÔÚ×ø±êÖáÉϽ¨Á¢Æ½ºâ·½³Ì½øÐнâ´ð£®ÔËÓö¯Äܶ¨Àí½âÌâʱ£¬Ê×ÏÈҪѡȡÑо¿¹ý³Ì£¬È»ºó·ÖÎöÔÚÕâ¸öÔ˶¯¹ý³ÌÖÐÄÄЩÁ¦×öÕý¹¦¡¢ÄÄЩÁ¦×ö¸º¹¦£¬³õÄ©¶¯ÄÜΪ¶àÉÙ£¬¸ù¾Ý¶¯Äܶ¨ÀíÁз½³Ì½â´ð£®
A£® | µ¯Á¦Ôö´ó£¬Ä¦²ÁÁ¦Ôö´ó | B£® | µ¯Á¦²»±ä£¬Ä¦²ÁÁ¦Ôö´ó | ||
C£® | µ¯Á¦Ôö´ó£¬Ä¦²ÁÁ¦²»±ä | D£® | µ¯Á¦²»±ä£¬Ä¦²ÁÁ¦²»±ä |
A£® | µç¶¯»úÏßȦµç×èΪ1¦¸ | B£® | µÆÅÝÕý³£·¢¹âʱµçÁ÷±íʾÊý0.5A | ||
C£® | µÆÅÝÕý³£·¢¹âʱµçÁ÷±íʾÊý1A | D£® | µç¶¯»úÊä³öµÄ»úе¹¦ÂÊ4.25W |
A£® | Ô˶¯µ½Pµã·µ»Ø | B£® | Ô˶¯µ½PºÍP¡äµãÖ®¼ä·µ»Ø | ||
C£® | Ô˶¯µ½P¡äµã·µ»Ø | D£® | ´©¹ýP¡äµã |
A£® | a×î´ó | B£® | b×îС | C£® | c×î´ó | D£® | Ò»Ñù´ó |
A£® | ÎïÌåÊܵ½µÄºÏÍâÁ¦Ô½´ó£¬ËٶȵĸıäÁ¿¾ÍÔ½´ó | |
B£® | ÎïÌåÊܵ½µÄºÏÍâÁ¦²»ÎªÁãÇÒ²»±ä£¬ÎïÌåµÄÔ˶¯×´Ì¬»á¸Ä±ä | |
C£® | ÎïÌåÊܵ½µÄºÏÍâÁ¦¸Ä±äÇÒ²»ÎªÁ㣬ÎïÌåµÄËٶȲ»Ò»¶¨¸Ä±ä | |
D£® | ÎïÌåÊܵ½µÄºÏÍâÁ¦²»ÎªÁãÇÒ²»±ä£¬ÎïÌåµÄÔ˶¯×´Ì¬¾Í²»¸Ä±ä |
A£® | µçÁ÷·½Ïò½«·¢Éú¸Ä±ä | B£® | ´ÅͨÁ¿µÄ±ä»¯ÂÊ´ïµ½×î´óÖµ | ||
C£® | ͨ¹ýÏßȦµÄ´ÅͨÁ¿´ïµ½×î´óÖµ | D£® | ´ÅͨÁ¿µÄ±ä»¯ÂÊ´ïµ½×îСֵ |