A horizontal force of 4,N is needed to keep a block of mass 0.5, kg sliding on a horizontal surface

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4-2.Friction

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A horizontal force of $4\,N$ is needed to keep a block of mass $0.5\, kg$ sliding on a horizontal surface with a constant speed. The coefficient of sliding friction must be :- $[g = 10\, m/s^2]$

A

$0.25$

B

$0.5$

C

$0.8$

D

$0.6$

Solution

For sliding the block

$\mathrm{F}_{\mathrm{ext}}=\mathrm{F}_{\mathrm{r}} \Rightarrow \mathrm{F}_{\mathrm{ext}}=\mu \mathrm{mg}$

$\Rightarrow \mu=\frac{F_{e x t}}{m g}=\frac{4}{0.5 \times 10}$

$\Rightarrow \mu=0.8$

Standard 11

Physics

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