Are root directly in contact with water?

A block of wood of dimension 20cmxx10cmxx5cm floating on water such that surface of maximum area is contact with water. What extra force, (over its weight) is required to just deatech the block from water surface given that surface tension of water is 72 dyne/cm.

In the manufacture of sulphuric acid by the contact process, sulphur trioxide is not directly dissolved in water. Why?

(A) : The viscous force, air resistance etc., are examples of contact force (R) : Contact force on an object arises due to contact with some other object

As functioning of smooth muscles can't be directly controlled, they are

Adrenaline directly affects

The method of irrigation in which the water reaches the root of the plant directly is