There are many factors which contributes as to how a machine will be processing the input energy and convert it to output energy. Even with identical mechanism, these factors will have major effect on the output. Some factors are deflection, friction and wear. Some system maybe exposed to poor lubrication than the other which'll produce more friction and wear thus lower mechanical advantage.
Answer: object B is negatively charged, object C is positively charged and object D is also positively charged
Explanation: since unlike charges attract and like charges repel, for object A which is positively charged and B to attract B must be negatively charged and then for B which is negatively charged and C to attract C must be positively charged and for C and D to repel they have to be of thesame charge which means D is positive as well.
An electric generator is when a magnet is rotated through a coil of wire to produce an electric current.
Cm^3 is same as mL
13.5 g / 5 mL = 2.7 g/mL
look up densities of metals
aluminum has a density of 2.7 g/mL