For every action there is an equal and opposite reaction." So that applies to a roller coaster, between the ride vehicles and the track. When a ride goes up and down the hill, it creates different forces onto the track.
Pluto is the last planet discovered in our solar system.
Answer:
Part a)

Part b)

Explanation:
As we know that electric force on electric charge is given as

here we have

E = 153 N/C
now force is given as

Gravitational force on electric charge near surface of earth is given as


now the ratio of two forces is given as


Part b)
Now the ball is balanced by the electric force and the force of gravity on it
so here we have



here we have
