The energy the person exerts to raise himself up h would cause the bag of sand to move up h, since he would be exerting a force F, which would just cause the bag of sand to move up, while he remained in one place
When you start applying it to force and other equations, i you get a negative answer then you know its an attractive force, if its a positive answer its a repulsive force. Yes, calling electrons negative and protons positive is arbitrary, but they need to be positive and negative, not one unit...
3 identical masses and four identical springs are set up as shown (m=mass ~=spring |=fixed point)
the two outside masses are displaced equally inwards. What is the effective spring constant of this system.
attempt at solution:
using FBDs F=-2kx on each individual outside mass