The electric field at a distance of 2 mm from a test charge is the field at a distance of 4 mm

a. same as
b. twice as strong
c. four times as strong
d. half as strong
e. one fourth as strong

Which two objects have the greatest gravitational force acting between them

Two identical 82 mg dust particles very far apart (pee 0) are moving directly toward each other at a speed of 3698 m/s. the charge on each is-719 ? c. determine how close they will get to each other. let k = 9x109 n-m2/c2 & ignore gravity.

An insulated 40 ft^3 rigid tank contains air at 50 psia and 120°f. a valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. the air temperature during this process is kept constant by an electric resistance heater placed in the tank. determine the electrical work done during this process.