Final answer:
The net force acting on the ball as it rolls down the hill is 9.0 N, calculated using Newton's second law of motion and the acceleration of the ball.
Step-by-step explanation:
To find the net force acting on a ball rolling down a hill, it's necessary to use the equation that relates force, mass, and acceleration (Newton's second law of motion): F = ma, where F is force in newtons (N), m is mass in kilograms (kg), and a is acceleration in meters per second squared (m/s2). First, calculate the acceleration (a) using the formula for acceleration: a = (v - u) / t, where v is the final velocity, u is the initial velocity (0 m/s since the ball starts from rest), and t is the time taken. So, the acceleration a is (20.0 m/s) / (10.0 s) = 2.0 m/s2. Now, applying the ball's mass (4.5 kg), the net force is F = ma = (4.5 kg) * (2.0 m/s2) = 9.0 N.