Subject:
A rope having a total mass of 0.4kg and total length 4m has 0.6m of the rope hanging vertically down off a work bench. How much work must be done to place all the rope on the bench? This one is very easy: First you assume that the rope is uniform, so the center of mass for the hanging pies is located at the half distance, namely 0.3m below the bench. And the mass of the entire hanging piece is 0.4/4*0.6 = 0.06kg. Now the work done by pulling the rope is exactly the same as pulling an object with mass of 0.06kg up 0.3m, hence the work is W=mgh = 0.06*9.8*0.3 = 0.176J Answer: 0.176 J A particle is trapped in an infinite one-dimensional well of width 0.132nm. The electron is in the n=10 state. A) What is energy of the electron? B) What is the uncertainty in its momentum?
