why is force attractive when the separation between body and force increases and potential increases and vice versa?

why is force repulsive when separation between body and force increases and potential decreases?

if PE/force is negative why attraction and if PE/force is positive why there is repulsion?

pls explain and prove the above points with suitable examples.

Asked by kaziryan.05 | 22nd May, 2021, 11:38: AM

Expert Answer:

Let me explain above statements first .
 
By definition , potential energy of an object at a point is workdone to bring the object
from infinity to the required point in the given force field.
 
If force field is repulsive, then work has to be done by external agency on the object
to bring the object from infinity to the required point.

If work is done externally on the object then work is positive, potential energy is also positive.
 
For example if positive source charge is placed at origin, to bring another positive test charge
from infinity to a point P, external work has to be performed on positiveve test charge.
Then potential energy at point P is positive .
 
This explains the first statement.
 
If force field is attractive , work is done by force field on the object to bring the object
from infinity to a required point.
 
If work is done by force field  on the object then work is negative, potential energy is also negative.
 
For example if positive source charge is placed at origin, to bring a negative test charge
from infinity to a point P, Force field due to positive charge at origine has performed the work on
negative test charge. Then potential energy at point P is negative .
 
This explains the second statement.
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Answered by Thiyagarajan K | 23rd May, 2021, 05:16: PM