Question

A block of weight 200N is pulled along a rough horizontal surface at constant speed by a force 100N acting at an angle ${30}^0$ above the horizontal. The coefficient of friction between the block and the surface is:

• A. 0.43
• B. 0.58
• C. 0.75
• D. 0.85

Answer 1

Answer: (B)

0.58

According to question,

As shown in below figure

So,The force on the block long the horizontal is

$F_x=100\cos 30-f\cdots \left(i\right)$

$f=\mu \times N\cdots \left(ii\right)$

and also,

$200=N+100\sin 30$

$N=150N$

Now,

substituting the above value in $\left(ii\right)$

$f=150\times \mu$

substituting the value of ${}^{\prime }{f}^{\prime }$ in $\left(i\right)$

$F_x=100\cos 30-150\times \mu$

Hence, the block moves with the constant velocity it means that there is no net force acting on it is horizontal direction,

$F_x=0$

$100\cos 30-150\times \mu =0$

$86.6025=150\times \mu$

$\mu =0.57735$