Answer:
Shearing stresses are the stresses generated in any material when a force acts in such a way that it tends to tear off the material.
Generally the above definition is valid at an armature level, in more technical terms shearing stresses are the component of the stresses that act parallel to any plane in a material that is under stress. Shearing stresses are present in a body even if normal forces act on it along the centroidal axis.
Mathematically in a plane AB the shearing stresses are given by

Yes the shearing force which generates the shearing stresses is similar to frictional force that acts between the 2 surfaces in contact with each other.
Please add more details because I don’t know if you are using a book or passage, therefore I cannot help you unless you add more detail
This is a very very difficult one for me, let me get back to you with the proper answer.
Answer:
answer is
a)
3/4
Explanation:
In the last 5 meters of braking, you lose 3/4 of your speed.