When you start sliding the couch, you have to overcome the static friction of the carpeted floor, which is usually very big, especially due to the texture of the carpet. However, as long as you get it moving, you only have to apply the force to overcome the kinetic friction, which is smaller than the static friction.
a) the cross-sectional area of the hose would be the square of radius times pi. And since the sectional radius is half of its diameter d. We can express the cross-sectional area A1 in term of diameter d1
