Find the efficiency of a device that needs 160 J of energy to produce 75 J of energy

that would be because of both gravity and friction. so     c

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.

energy stored in the capacitor= 9.72 x 10⁻⁴ j

explanation:

the energy stored in the capacitor is given by

e= 1/2 c v²

e= energy stored

c= capacitance= 1.5 µc= 1.5 x 10⁻⁶f

v= potential difference=36 v

so energy stored= e= 1/2 (1.5 x 10⁻⁶) (36)²

energy stored= 9.72 x 10⁻⁴j