A ball rolling down a hill with a speed of 8 m/s has 139 J of kinetic energy. What is it's mass in kg?

Electric charge is uniformly distributed inside a nonconducting sphere of radius 0.30 m. the electric field at a point p, which is 0.50 m from the center of the sphere, is 15,000 n/c and is directed radially outward. what is the maximum magnitude of the electric field due to this sphere

What color would an object that reflects green and blue light appear to be in white light? a. blue b. cyan c. magenta d. black

Imagine you had to physically add electrons, one at a time, to a previously neutral conductor. you add one electron very easily, but the second electron requires more work. in your initial post to the discussion, explain why this is. also, what happens to the work needed to add the third, fourth, fifth, and subsequent electrons