Question

A block is at rest on inclined plane making an angle
30° with the horizontal. As the angle of the inclined
plane is increased, the block just starts slipping when
the angle of inclination becomes 45°. The coefficient
of static friction between the block and surface of in-
clined plane is
(1) 13
(2) J2
1
(3) TE
(4) 1
AC​

Answer 1

Answer:

Correct option is (C)

Explanation:

tanθ

Forces normal to the plane are balanced as the block cannot move normal to the plane.

N=mgcosθ ... (i)

When the body just begins to slide, forces parallel to the plane are balanced.

F

r

=mgsinθ ...(ii)

Frictional force acting when the body just begins to slide is given by:

F

r

=μN .... (iii)

Substituting (i) & (iii) in (ii), we get

μmgcosθ=mgsinθ

μ=tanθ