What are the social factors in using solar energy?

Using Work and Energy to Calculate Tension ?

• Using Work and Energy to Calculate Tension; Consider the Atwood's machine shown in the figure , with = 1.5 , = 3.3 , and = 4.5 . In this problem, we show how to calculate the tension in the rope using energy and work, rather than Newton's laws. B) Use energy conservation applied to the entire system to calculate the change in mechanical energy for block 2 as it drops through the height. C) Use your answer to part B, and the known drop height, to find the magnitude of the tension in the rope. http://session.masteringphysics.com/problemAsset/1123718/2/Walker4e.ch08.Pr099.jpg

• Answer:

  B) Let mass of block to m2 be denoted by M and m1 by m. Energy conservation gives us -Mgh + ½Mv² + mgh + ½mv² = 0 ---------------------------------- 1 This gives v² = [{2gh(M-m)}/(M+m)] ----------------------------------------… 2 [LHS is change in mechanical energy of Block 2 (net decrease) and RHS is the change (increase of mechanical energy of the block 1] C) Gain in KE of block 1 from equation 2 = ½mv² = [{mgh(M-m}/(M+m)] = [T-mg]*h by Work-energy theorem So T = mg[1+ {(M-m)}/(M+m)} = {(2M)/(M-m)}mg Using the values m = 1.5 kg, M= 3.3 kg and h = 4.5 m, we get T s T = (1.5*9.81)*{(2*3.3)/(3.3-1.5)} = 53.955 or 54 N