What keeps the protons in an atomic nucleus from flying away from one another

What are two different ways you could find the value of a? explain these methods.

A0.580-kg rock is tied to the end of a string and is swung in a circle with a radius of 0.500 meters. the velocity of the rock is 4.50 m/s. what is the centripetal force acting on the rock? 15.5 n 5.22 n 69.8 n 23.5 n

Which of the following are appropriate acceleration units?