Answer;
1. strong nuclear force
2. electromagnetic force/ electric force
Explanation;
The more protons an element has, the harder it is to bring nuclei together. It takes more energy to trigger fusion in iron and other heavy elements. Lighter elements, such as helium and hydrogen, require less energy to bring about fusion. The sun, for instance, spends most of its life converting hydrogen into helium.
-The strong nuclear force depends on; a more massive the object is the more attractive the force produced and also as distance between objects increases, attractive force decreases at a faster rate.
