A wooden block is kept on a polished wooden plank and the inclination of the plank is gradually increased. It is found that the block starts slipping when the plank makes an angle of 18° with the horizontal. However, once started the block can continue with uniform speed if the inclination is reduced to 15°. Find the coefficient of static friction between the block and the plank.
(a) tan 18^0
(b) tan 15^0
(c) tan 33^0
(d) tan 3^0
The question was posed to me in an internship interview.
The query is from Laws of Solid Friction and Limiting Friction in chapter Friction of Machine Kinematics