If all of the forces acting on an object balance so that the net force is zero, then
(a) the object must be at rest
(b) the object’s speed will decrease
(c) the object will follow a parabolic trajectory
(d) the object’s direction of motion can change, but its speed cannot
(e) none of the above

Asmall 12.00g plastic ball is suspended by a string in a uniform, horizontal electric field with a magnitude of 10^3 n/c. if the ball is in equilibrium when the string makes a 30 ° angle with the vertical, what is the net charge on the ball?

Sally turns on her cellular telephone to speak to her friend who is located thousands of miles away. which of the following best describes how such a telephone is able to transmit and receive information? a. the cellular telephone transmits, receives, and encodes information using only sound waves. b. the cellular telephone transmits, receives, and encodes information using only electromagnetic waves. c. the cellular telephone transmits information by electromagnetic waves to a receiver which then encodes them and produces sound. d. the cellular telephone transmits information by sound waves to a receiver which then encodes them and produces electromagnetic waves.

How many excess electrons must be present on each sphere if the magnitude of the force of repulsion between them is 4.57×10−21 newtons?