Final answer:
The momentum of a child and wagon with a total mass of 23 kg and a velocity of 1.75 m/s is 40.25 kg m/s, which is option (a).
Step-by-step explanation:
The momentum of an object can be calculated by the formula momentum = mass × velocity. So for the child and wagon with a total mass of 23 kg and a velocity of 1.75 m/s, the momentum can be calculated as follows:
Momentum = 23 kg × 1.75 m/s
Momentum = 40.25 kg·m/s
So the correct answer to the student's question is 40.25 kg m/s, which corresponds to option (a).