1. The problem statement, all variables and given/known data An empty wagon with mass 10 kg is pulled by a force of 75 N at a constant speed. Rain falls collecting in the wagon at a rate of 375mm^3/s. The density of water is 1g/mm^3. A) Make a table showing how much force must be exerted on the wagon to keep it moving at a constant speed for 10 seconds. Graph it. B)Find the average force exerted on the wagon over this 10 second period. C)What is the impulse over these 10 seconds? 2. Relevant equations mass of wagon at time t (seconds) in kg=10+0.375t F(net)=ma 3. The attempt at a solution If the wagon is moving at a constant speed, then all forces must be balanced. So the 75 N force must be balanced by a friction force also of 75 N. The equation for mass of the wagon was simple enough to derive but im stuck at this part. Is this a trick question? Because the way i see it is that no aditional force is required to keep it moving at a constant speed. As long as the 75 N force was continued and balanced by the friction force, wouldnt the cart continue to move at a constant speed forever no matter how much mass was gained from the rain? So the average force exerted on the wagon would just be 75 for 10 seconds and therefore the impulse would be 750. Or does the 75 N force not even count as an exerted force since its balanced and the actual answer is 0?