Answer:
The gravitational potential energy of the nickel at the top of the monument is 8.29 J.
Explanation:
We can find the gravitational potential energy using the following formula.

Identifying given information.
The nickel has a mass
, and it is a the top of Washington Monument.
The Washington Monument has a height of
, thus we need to find the equivalence in meters using unit conversion in order to find the gravitational potential energy.
Converting from feet to meters.
Using the conversion factor 1 m = 3.28 ft, we have

That give u s

Finding Gravitational Potential Energy.
We can replace the height and mass on the formula

And we get


The gravitational potential energy of the nickel at the top of the monument is 8.29 J.
The first: alright, first: you draw the person in the elevator, then draw a red arrow, pointing downwards, beginning from his center of mass. This arrow is representing the gravitational force, Fg.
You can always calculate this right away, if you know his mass, by multiplying his weight in kg by the gravitational constant

let's do it for this case:

the unit of your fg will be in Newton [N]
so, first step solved, Fg is 637.65N
Fg is a field force by the way, and at the same time, the elevator is pushing up on him with 637.65N, so you draw another arrow pointing upwards, ending at the tip of the downwards arrow.
now let's calculate the force of the elevator

so you draw another arrow which is pointing downwards on him, because the elevator is accelating him upwards, making him heavier
the elevator force in this case is a contact force, because it only comes to existence while the two are touching, while Fg is the same everywhere
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.