Final answer:
The net force acting on a ball with a mass of 4.5 kg accelerating to 20.0 m/s in 10.0 seconds is 9.0 N, which is calculated using Newton's second law of motion.
Step-by-step explanation:
The student is asking about the net force acting on a ball as it accelerates down a hill. To find the net force, the formula from Newton's second law of motion, F = ma (force equals mass times acceleration), can be used. Given that the ball has a mass of 4.5 kg and it accelerates from rest to a speed of 20.0 m/s in 10.0 seconds, we first need to calculate the acceleration using the formula a = ∆v / ∆t (acceleration equals change in velocity over change in time).
Acceleration (a) = ∆v / ∆t = 20.0 m/s / 10.0 s = 2.0 m/s².
Using Newton's second law, the net force (F) on the ball is:
F = ma = 4.5 kg × 2.0 m/s² = 9.0 N.
Therefore, the correct answer is (a) 9.0 N.