Hi guys, I need some assistance on the following. 1) You need to push a 30kg mass up an inclined slope of 30 degrees from rest. After moving it by 5m and creating 600J of energy due friction in the process, you find that the mass is moving at 1 m/s. Find the work done moving the mass over the distance of 5m. I have: sin30(30)(10) = 150N. 600 = F x 5 => F= 120N. So the av. net force is 30N. So 30 X 5 = 150J. However this is not one of the choices'. Where is the mistake? 2) 2 objects A and B are separated by a finite distance R and act on each other through their g field. If mass A is doubled and distance R tripled, what happens to their gravitational potential? I'm not sure how to start here. Anyone? 3) Which of the following condtions is not necessary for lgiht waves from 2 sources to intefere? a) They must have same wavelength b) They must have same frequency c) They must have same amplitude d) They must have a constant phase difference e) all above are necessary More than 1 options allowed. I chose amplitude. However, do they need to have a constant phase diff? 4) If the distance of the plates of a capacitor is increased, will the energy stored in it be the same, increase or decrease? Is a capacitor supposed to have small internal resistance or a large one? I would say the same as there is no relation of the distance of the plates with its energy? For part 2 I'm not sure. 5) Why does the binding energy per nucleon does not depend on the volume of the nucleus? I only know binding energy is the energy required to separate the individual nucleons. I'm not sure why. Any help appreciated! Thanks!