Metal sphere a has a charge of -2 units and an identical sphere b has a charge of -4 units. if the two spheres are brought together and then separated, the charge on sphere a will
a) -3 units
b) +4 units
c) 0 units
d) -2 units
*if you can also explain how this is done when answering that would be great : )

Modern physics a photon emitted from an excited hydrogen atom has an energy of 3.02 electron volts. which electron energy-level transition would produce this photon? a. n=1 to n=6 b. n=2 to n=6 c. n=6 to n=1 d. n=6 to n=2 i chose b but the correct answer is d can someone tell me why? and what's the difference?

The electronic structure or chlorine is 2.8.7 what is the electronic structure of fluorine?

A2000 kg car is rounding a curve of radius 200 m on a level road. the maximum frictional force the road can exert on the tires of the car is 4000 n. what is the highest speed at which the car can round the curve?