Question

A block slides down an inclined surface of inclination ${30}^{\circ }$ with the horizontal. Stating from rest it covers 8 m in the first two seconds. The coefficient of kinetic friction between the blocks and surface is:

• A. 0.11
• B. 0.22
• C. 0.33
• D. 0.44

Answer 1

The correct option is A 0.11

$\begin{array}{c}acceleration=\left(g\sin {30}^0-\mu \cos {30}^0\right)\\ 8=\frac{1}{2}\left(a\right)t^2\\ \Rightarrow 8=\frac{1}{2}\left[\frac{g}{2}-\frac{\mu g\sqrt{3}}{2}\right]\times 4\\ \Rightarrow 8=g-\mu g\sqrt{3}\\ \Rightarrow 8=10\mu \sqrt{3}\\ \mu =\frac{2}{10\sqrt{3}}\\ =0.11\\ Hence,\\ optionAiscorrectanswer.\end{array}$