What does newtons first law of motion say about objects in motion?

A100 kg running back runs at 5m/s into a stationary linebacker. it takes 0.5 for the running back to be completely stopped

For those who need theses answers i just took the test and got everyone of them

Ascientist is working with a new kind of quantum dot to make a dye. he is applying newton’s laws to the particle, but it seems to be breaking these laws of physics. which action will most likely the scientist study the particle’s motion? a. he needs to remember that the particle is too large for quantum analysis. b. he must continue to use newtonian mechanics, but he needs to learn more about the particle. c. he needs to use quantum mechanics, not newtonian mechanics, because this is a nanotechnology product. d. he must determine new physical laws that only apply to quantum dots.