Expand each vector into their component forms:
Similarly,
Then assuming the resultant vector 
is the sum of these three vectors, we have
and so has magnitude
and direction 
such that
the answer is heat engine
Answer:
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.
A. A car comes equipped with side airbags. I don't know how I'm supposed to show work but that's the answer
