http://sgforums.com/forums/2297/topics/316884 en-US 60 <p>thanks, confirms what ive done is correct</p> Wed, 14 May 2008 17:40:02 +0800 sgforums.com:2297:316884:8086218 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>Q2</p> <p>Reaction force = mg cos 54 + mrω^2 = m * (5.766 + 18.28224) = 24.0484 m</p> <p>let coefficient of static friction be μs</p> <p>μs *&nbsp; 24.0484 m = mg sin 54<br /> μs = 0.33</p> Wed, 14 May 2008 11:56:44 +0800 sgforums.com:2297:316884:8085226 eagle http://sgforums.com/forums/2297/topics/316884 <p>Q1</p> <p class="">Assume it is moving already... If it is not, we have to redo with μs... So now we do with μk</p> <p class="">Let the tension in the string be T</p> <p class=""><span style="text-decoration: underline;">For the 54kg block,</span><br /> Reaction force is 54g cos 42<br /> Downward force is 54g sin 42</p> <p class="">Taking moving downwards left as positive,<br /> 54 * a = 54g sin42 - T - μk 54g cos42<br /> 54a = 315.0979 - T -- (1)</p> <p class=""><span style="text-decoration: underline;">For the 27kg block,<br /></span>upward force = T<br /> downward force = 27g<br /> <br /> Taking upwards as positive,<br /> T - 27g = 27a<br /> 27a = T - 264.87<br /> 54a = 2T - 529.74&nbsp; -- (2)</p> <p class="">(2) - (1): 3T - 844.8779 = 0<br /> T = 281.626N</p> Wed, 14 May 2008 11:36:33 +0800 sgforums.com:2297:316884:8085165 eagle http://sgforums.com/forums/2297/topics/316884 <p>for q2:</p> <p>&nbsp;</p> <p>Us = g sin T / (w^2 r + g cos T)<br /></p> Tue, 13 May 2008 20:32:39 +0800 sgforums.com:2297:316884:8083942 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>far out im tank.</p> <p>&nbsp;</p> <p>derived<br /> acceleration of the block = a = (mg + uk Mgcos # - Mgsin# )/(M+m) and the T = mg - ma<br /> <br /> # = the given angle<br /> M = the greater mass<br /> m = the smaller mass<br /> uk = the given kinetic coefficient of friction</p> <p>&nbsp;</p> <p>so answer for first bit should be 281.6126N</p> <p>&nbsp;</p> <p>okay second question...</p> Tue, 13 May 2008 19:37:48 +0800 sgforums.com:2297:316884:8083826 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>help D:?</p> <p>the force pulling the block up is the same as the one going down?</p> Mon, 12 May 2008 14:30:04 +0800 sgforums.com:2297:316884:8080703 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>mass times friction coefficient to test slipping... or is it force. it should be mass :x ahh wth</p> Sat, 10 May 2008 19:42:10 +0800 sgforums.com:2297:316884:8076256 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>okay.. i lost some marks for the first question.. still wrong :x</p> <p>im not sure about the second question</p> Fri, 09 May 2008 21:12:00 +0800 sgforums.com:2297:316884:8074151 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>ok :s</p> <p>add: wah cert x)</p> Thu, 08 May 2008 21:36:02 +0800 sgforums.com:2297:316884:8071631 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884 <p>first question is JC physics with friction added only</p> <p>2nd question need to consider force</p> <p>In short, you need to draw out all the forces to analyse.</p> <p>&nbsp;</p> <p>Try first... Cannot do tmr I do... my last paper tmr... after wait for my first class cert only :D</p> Thu, 08 May 2008 19:00:53 +0800 sgforums.com:2297:316884:8071327 eagle http://sgforums.com/forums/2297/topics/316884 <p>this looks harder than what i normally do &gt;.&lt;</p> <p><img src= "http://i105.photobucket.com/albums/m225/nickykeeng/album2/jf.jpg" alt="" /></p> Thu, 08 May 2008 18:43:41 +0800 sgforums.com:2297:316884:8071300 WoAiMeiMei http://sgforums.com/forums/2297/topics/316884