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Standard XII

Physics

Finding Friction's Magnitude

A body of mas...

Question

A body of mass $5 k g$ is kept on a rough horizontal surface. It is found that the body does not slide if a horizontal force less than $30 N$ is applied to it. Also it is found that it takes $5 s e c o n d s$ to slide throughout the first $10 m$ if a horizontal force of $30 N$ is applied and the body is gently pushed to start the motion. Taking $g = 10 m / s^{2}$ , calculate the coefficients of static and kinetic friction between the block and the surface.

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Solution

$30 = μ_{s} m_{g}$

$μ_{s} = \frac{30}{50} = 0.6$

$s = \frac{1}{2} a t^{2} \Rightarrow a = \frac{2 \times 10}{25} = 0.8$

$μ_{k} = \frac{30 - m \times 0.8}{m_{g}}$

$= \frac{30 - 4}{50} = \frac{26}{50} = 0.52$

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30=μsmgμs=3050=0.6s=12at2⇒a=2×1025=0.8μk=30−m×0.8mg=30−450=2650=0.52

$30 = μ_{s} m_{g}$

$μ_{s} = \frac{30}{50} = 0.6$

$s = \frac{1}{2} a t^{2} \Rightarrow a = \frac{2 \times 10}{25} = 0.8$

$μ_{k} = \frac{30 - m \times 0.8}{m_{g}}$

$= \frac{30 - 4}{50} = \frac{26}{50} = 0.52$