12.4 Exercise 5

(a) Calculate the retarding force due to the viscosity of the air layer between a cart and a level air track given the following information—air temperature is $\text{20}º\text{ C}$, the cart is moving at 0.400 m/s, its surface area is $2 . \text{50} \times \text{10}^{−2} \text{m}^{2}$, and the thickness of the air layer is $6.00 \times \text{10}^{- 5} \text{m}$. (b) What is the ratio of this force to the weight of the 0.300-kg cart?