Adhesive.
Adhesive is the force of attraction between molecules of different kind. Liquid flows upward the wick because the adhesive force between the wick and the liquid is higher than cohesive forces in the liquid.
When the adhesive force between the wick and the liquid is high we have capillarity taking place. This cause the liquid to move up the wick.
Work in general is given by W=F·d where F is the force vector and d is the displacement vector. The dot symbol is the dot product which is a measure of how parallel two vectors are. It can be replaced by the cosine of the angle between the two vectors and the vectors replaced by their magnitudes. If F and d are parallel then the angle is zero and the cosine is unity. So in this case work can be defined as the product of the magnitudes of the force and distance:
W=Fd
Answer:
a) F = 18.375N, b) F = 24.5 N
Explanation:
This exercise can be solved using the translational equilibrium equations.
Let's start by fixing a reference system with the horizontal x axis and the vertical y axis, from the statement of the exercise I understand that the wall is vertical and the book is supported on it, therefore the applied force is in the direction towards the wall
a) In this part the force that does not allow the movement of the book is requested, therefore the static friction coefficient must be used (μ_s = 0.8)
X axis
F - N = 0
N = F
Y axis
fr - W = 0
W = fr
where W is the weight of the book.
The friction force has the formula
fr = μ_s N
we substitute
mg = μ_s F
F = ![\frac{mg}{\mu_s }](https://tex.z-dn.net/?f=%5Cfrac%7Bmg%7D%7B%5Cmu_s%20%7D)
let's calculate
F = 1.5 9.8 / 0.8
F = 18.375N
b) In this case the book is moving so the friction coefficient to use is kinetic ( μ_K = 0.6)
F = ![\frac{mg}{\mu_K }](https://tex.z-dn.net/?f=%5Cfrac%7Bmg%7D%7B%5Cmu_K%20%7D)
we calculate
F = 1.5 9.8 / 0.6
F = 24.5 N