a freight train is traveling with a speed of 18.0m/s begins braking as it approaches the station. it takes 23s to stop what is the acceleration of the train?

The graph describes the motion of an object. the object moves with from a to b. it from b to c. it moves with from c to d.

30 points - when can a theory be modified if a new type of technology allows for new observations that raise new questions? a. immediately, while the questions about the theory are being asked b. after new hypotheses related to the theory are tested in experiments c. only after the new observations disprove all parts of the theory d. while scientists begin to think about how the theory could improve

The protons in a nucleus are approximately 2 ✕ 10^−15 m apart. consider the case where the protons are a distance d = 1.93 ✕ 10^−15 m apart. calculate the magnitude of the electric force (in n) between two protons at this distance.