FrictionHard
Question
A plank is held at an angle a to the horizontal (Fig.) on two fixed supports A and B. The plank can slide against the supports (without friction) because of its weight Mg. With what acceleration and in what direction, a man of mass m should move so that the plank does not move.
Options
A.g sin α 
down the incline
down the incline B.g sin α up the incline
up the incline C.g sin α 
down the incline
down the incline D.g sin α up the incline
up the incline Solution
For plank be at rest, applying Newton′s second law to plank along the incline
Mg sin α = f ....................................(1)
and applying Newton′s second law to man along the incline.
mg sin α + f = ma ....................................(2)
a = g sin α
down the inclineAlternate Solution :
If the friction force is taken up the incline on man, then application of Newton′s second law to man and plank along incline yields.
f + Mg sin α = 0 ..........(1)
mg sin α α f = ma ..........(2)
Solving (1) and (2)
a = g sin α
down the inclineAlternate Solution :
Application of Newton′s seconds law to system of man + plank along the incline yields
mg sin a + Mg sin a = ma
a = g sin α
down the inclineCreate a free account to view solution
View Solution FreeMore Friction Questions
A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes ...A system is shown in the figure, which is released from rest. There is no friction between ground and mass 5m. The coeff...In the arrangement shown, horizontal surface is smooth, but friction is present between the block and the surface of the...The coefficient of friction between the block and the horizontal surface is μ as shown in figure. The block moves t...A uniform chain has mass M and length L. If is placed on a frictionless table with length l0 hanging over the edge. The ...