Physics Help Forum Finding minimum values for problems

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Aug 2nd 2013, 05:05 PM #1 Junior Member   Join Date: Aug 2013 Posts: 2 Finding minimum values for problems Hi guys, really stuck on this one. A 1000N black is to be lifted using a chain sling (as shown). If the tension in the chain sling is not to exceed 1300N, find the shortest sling ABC that can be used. A is the most left point, B is the most right point and C is the top point. I think i have to take the derivative of something to find the minimum but have no idea how to go about that.
 Aug 3rd 2013, 04:17 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,344 No derivatives needed at all - this problem is easier than you think. To lift the bar the vertical component of force applied by the chain at each end is 1/2 the bar's weight, or W/2. But there is also a horizontal component of force as well, since a chain lifts by tension and tension acts only in the direction of the chain. If T is the tension in the chain, and theta is the angle of the chain to the bar, then T sin(theta) = W/2 From geometry to get the shortest chain possible you want theta to be small. But note that as theta goes from large to small values the value of T gets bigger. You've been given a max value of T, so now you can determine what the corresponding value for theta is, and from that the length of the chain.
 Aug 3rd 2013, 03:28 PM #3 Junior Member   Join Date: Aug 2013 Posts: 2 Ohhhh. Thank you so much man!

 Tags finding, minimum, problems, values

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post ling233 Light and Optics 2 Sep 23rd 2014 02:13 AM njuice8 Kinematics and Dynamics 2 Feb 19th 2013 03:03 AM cMTOXIN Thermodynamics and Fluid Mechanics 2 Feb 5th 2011 07:55 AM stealth Electricity and Magnetism 1 Feb 28th 2010 10:37 PM davefulton Thermodynamics and Fluid Mechanics 1 Feb 14th 2010 12:20 PM