Which contributions did Johannes Kepler make? Select three options. He revived Aristotle’s model of the solar system. He solved Ptolemy’s model by proving elliptical orbits. He proved Galileo’s calculations were incorrect. He determined that planets move faster when closer to the Sun. He discovered laws of planetary motion.

Ateacher attaches a ball to a meter long string and whirls it around in a horizontal circle at constant speed. the teacher explains that the string is what makes the ball go in a circle. why is the string necessary? a) the string is needed to apply a torque to the ball. b) the string is needed to push on the ball to get it up to speed. c) circle motion requires an inertia which is provided by the string. d) circle motion requires a force to give it a centripetal acceleratio