Answer:
Part A:
Part B:
Explanation:
<u> Part A:</u>
The potential energy at a point due to a charge is defined as
.
<em>where</em>,
V = electric potential at that point.
Therefore,
<u>Part B:</u>
Now, if the charge at that point is replaced with , then the electric potential energy at that point is given by
1) The braking force is provided by the frictional force, which is given by:
where
is the coefficient of friction
m=1500 kg is the mass of the car
is the gravitational acceleration
Substituting numbers into the equation, we find
2) The work done by the frictional force to stop the car is equal to the product between the force and the distance d:
(1)
where we put a negative sign because the force is in the opposite direction of the motion of the car.
3) For the work-energy theorem, the work done by the frictional force is equal to the variation of kinetic energy of the car:
(2)
The final kinetic energy is zero, so the variation of kinetic energy is just equal to the initial kinetic energy of the car:
4) By equalizing eq. (1) and (2), we find the distance, d: