Two equal positive charges are held in place at a fixed distance. If you put a third positive charge midway between these two charges, its electrical potential energy of the system (relative to infinity) is zero because the electrical forces on the third charge due to the two fixed charges just balance each other. True / False.

false

Explanation:

Given

Two equal positive charge are held in place at a fixed distance

Suppose q is charge and 2d is the distance between them

Suppose is the third charge which is placed d distance apart from q

Now the force by charge q will make the charge to move right while other charge cause the charge to move left.

Overall forces by charge q will cancel out each other

Now electrical Potential Energy

It is clear that

Therefore above statement is false.

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

read more on -