Final answer:
The acceleration of the shopping cart is 4.5 meters per second squared, calculated using Newton's second law with a net force of 90 N and the cart's mass of 20 kg.
Step-by-step explanation:
The question involves calculating the acceleration of a shopping cart given the force applied by Alice and the opposing force of friction. To solve this problem, we need to apply Newton's second law of motion, which is summarized by the equation F = ma, where F is the net force acting on an object, m is the mass of the object, and a is its acceleration.
Firstly, we need to calculate the net force acting on the cart by subtracting the force of friction (30 N) from the force applied by Alice (120 N). This gives us a net force of 90 N. Since the mass of the shopping cart is 20 kg, we can then find the acceleration by rearranging the equation to a = F/m.
Acceleration (a) = Net force (F) / Mass (m) = 90 N / 20 kg = 4.5 m/s2.
Therefore, the acceleration of the shopping cart is 4.5 meters per second squared.