Problem 21-40a:
the electric field near the surface of earth points downward and has a magnitude of 153 n/c. what is the ratio of the magnitude of the upward electric force on an electron to the magnitude of gravitational force on the electron?
2.74×1012
problem 21-40b:
what charge should be placed on a plastic ball of mass 5.25 g so that the electric force balances the weight of the ball near earth's surface?

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

a cold ice-tea.

pour in room temperature or cold water. cover the pitcher and refrigerate. steep white or green tea for 6 to 8 hours; steep black or oolong tea for 8 to 12 hours.jun 28, 2015