Question

a) State and explain law of reflection of sound
b) What is friction and how is its dependence with mass?

Answer 1

Dear Student,
a) The laws of reflection of sound are same as that of light.
The laws of reflection are:
(1) The angle of incidence is equal to the angle of reflection
(2) The incident wave, the normal, and the reflected wave, all lie in the same plane.
b) Friction -
Friction is the opposition force between surfaces that are in contact and are in motion with respect to one another.

The maximum force of static friction that exists between two surfaces is proportional to the normal force and mostly independent of area of contact. While the total normal force (force perpendicular to the horizontal surface) which is essentially the weight of the object does depends on the mass of the body.So mass plays an important role in causing friction.

Regards