1.A small 3.94 g plastic ball is suspended by a
27.9 cm long string in a uniform electric field
of 3400 N/C.
The acceleration of gravity is 9.8 m/s2 , and
the Coulomb constant is 8.99×109 N · m2/C2.
If the ball is in equilibrium when the string
makes a 43.2◦ angle with the vertical as in-...