The main reason astronomers have a difficult time trying to understand stellar evolution (ie. trying to understand the life cycle of a star) is because .

Which surface feature of the moon is characterized by mountainous areas? terrae craters maria regolith

How much force must a locomotive exert on a 12840-kg boxcar to make it accelerate forward at 0.490 m/s2?

Two vectors are shown. which statement best compares the vectors? vector x has greater magnitude than vector y. vector y has greater magnitude than vector x. the vectors have the same displacement. the vectors have the same direction.