How did ernest rutherford change the atomic model based on his experimental results? a. he placed electrons in orbits around the nucleus. b. he described the atom as a sea of positive charge sprinkled with electrons. c. he placed positive material in the atom's center. d. he described electrons as being in clouds outside the nucleus.

You have two answers that are pretty close. He mentioned D, but what he really found and stuck with it and concentrated on it when submitting his findings was that the nucleus of an atom was small and concentrated at the center of the atom.

So the answer is C but you cannot easily eliminate D. I think the question is somewhat faulty, but C should give you the mark.

C. He placed positive material in the atom's center.

Explanation:

Ernest Rutherford was a physicist from New Zealand who spent most of his career in England and Canada. Rutherford was an important figure in the history of the discovery of the atom. Rutherford is famous for his gold foil experiment. Based on the results of his experiment, Rutherford concluded that there must be a tiny volume of the atom, containing most of the atom's mass, at the center of the atom. This would have a positive charge, and the rest of the atom must be made of mostly empty space. This positive material in the atom's center is the nucleus.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.