Question
A block of mass 0.1 is held against a wall applying a horizontal force of $$5N$$ on the block. If the coefficient of friction between the block and the wall is 0.5, the magnitude of the frictional force acting on the block is :
A.
$$2.5N$$
B.
$$0.98N$$
C.
$$4.9N$$
D.
$$0.49N$$
Answer :
$$0.98N$$
Solution :
Limiting frictional force, $${f_l} = {\mu _s}N = 0.5 \times 5 = 2.5N.$$ But force tending to produce relative motion is the weight $$\left( W \right)$$ of the block which is less than $${f_l.}$$ Therefore, the frictional force is equal to the weight, the magnitude of the frictional force $$f$$ has to balance the weight $$0.98 N$$ acting downwards.
Limiting frictional force, $${f_l} = {\mu _s}N = 0.5 \times 5 = 2.5N.$$ But force tending to produce relative motion is the weight $$\left( W \right)$$ of the block which is less than $${f_l.}$$ Therefore, the frictional force is equal to the weight, the magnitude of the frictional force $$f$$ has to balance the weight $$0.98 N$$ acting downwards.
