Newton concluded that a force from the Earth had to act on the moon because
A) a force is needed to keep the moon in motion in its orbit.
B) a force is needed to pull the moon outward.
C) a force is needed to accelerate the moon toward Earth away from straight-line motion.
D) the moon moved at a constant velocity in a straight line.
E) all of the above.

Question

Quizplus · Accepted Answer

Newton concluded that a force is needed to accelerate the moon toward Earth away from straight-line motion, which is consistent with his law of universal gravitation and the concept of centripetal force required for circular motion.

Newton Concluded That a Force from the Earth Had to Act