Could someone check if I did this problem correctly?
A mover’s dolly is used to transport a refrigerator up a ramp into a house. The refrigerator has a mass of 115 kg. Te ramp is 2.1 m long and rises .850 m. The mover pulls the dolly with a force of 496 N up the ramp. The dolly and the ramp constitute a machine.
-What work does the mover do? I answered: 1041.6 J = (496)(2.1)
-What is the work done on the refrigerator by the machine? I answered: (115)(9.8)(2.1) = 2366.7 J
WHen i calculate the efficiency of the machine, i get over a 100. So i know i did the problem incorrectly. I just don’t know what.
Could some explain? ; _ ;
The error you have made is in the calculation of the work done on the refrigerator by the machine, which should be mgh. It should therefore be 1159*9.8*0.85 = 958.9275J – hence the machine is less than 100% effective as it should be to prevent a violation of the laws of thermodynamics.
Name (required)
Mail (will not be published) (required)
Website
