Ethan starts to pull the wagon across the yard. To move the wagon at the same speed each time, which friend does Ethan need to pull with a larger force?

 - a friend who weighs 21 pounds
 - a friend who weighs 28 pounds
Look for the friend who is heavier.
A friend who weighs 28 pounds is heavier than a friend who weighs 21 pounds. So, to move the wagon at the same speed each time, Ethan needs to use a larger force to start moving the wagon with a friend who weighs 28 pounds.