Question

A block of mass 5 kg is placed on a rough horizontal surface
of a moving compartment. It is seen by an observer sitting
inside the compartment, that a force of 10N is required in
horizontal direction to move the box in a direction parallel to
the motion of compartment while a force of 20N is required
in horizontal direction to move the box in opposite direction.
Coefficient of friction between the surface of the block and
the surface =A/10. Find A.
(a) I (b) 2 (c) 3 (d) 4.
1
efono​

Answer 1

Given that,

Mass of block = 5 kg

Force = 10 N

Force = 20 N in opposite direction

We need to calculate the friction

Using balance equation

$F_{1}+ma=f$...(I)

$F_{2}=f+ma$.....(II)

From equation (I) and (II)

$F_{1}+F_{2}=2f$

Put the value into the formula

$10+20=2f$

$f=15$

We need to calculate the value of A

Using formula of friction force

$f=\mu N$

$f=\mu m\times g$

$\mu=\dfrac{15}{5\times10}$

$\mu=\dfrac{3}{10}$

Hence, The value of A is 3.

(c) is correct option.