What are the two sources of earth's internal heat energy sunlight and radiation from space
motion and other forms of kinetic energy
cosmic rays and gravitational energy
radioactive decay and heat of formation

Hey

Your answer would be Radioactive Decay and Heat of formation.

When earth first formed it was very violant. Some planetary scientists believe that the moon was created from a collision involving earth and Thea (a theoretical dwarf planet). these collisions that have formed earth heated it so much that it is still hot from them.

Radioactivce decay is another major fource of internal heat for earth.

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s