Answer:
a)
, b)
, c)
.
Explanation:
a) Let assume that car travel on a horizontal surface. The equations of equilibrium of the car are:


After some algebraic handling, the following expression for the propulsion force is constructed:



b) The power require to move the car at a speed of 5 meters per second is:



c) The efficiency of the car is:


b is your answers in this thread
90 km/h is 25 m/s
the relative velocity when cars are traveling in opposite directions is the sum of the two
25+20= 45 m/s
The solution for this problem is computed by through this formula, F = kQq / d²Plugging in the given values above, we can now compute for the answer.
F = 8.98755e9N·m²/C² * -(7e-6C)² / (0.03m)² = -489N, the negative sign denotes attraction.