David delivers meals to elderly people once a week. He uses a cart to move the meals. The cart has four smooth wheels. Which type of friction acts between the cart wheels and the sidewalk?
A. sliding friction
B. rolling friction
C. fluid friction
D. static friction
Since the wheels roll, the wheels do not rub against the sidewalk, So it cannot be sliding. The wheels are not a liquid, and there shouldnt be any static.
