A block of mass 4,kg is placed on a rough horizontal plane A time dependent force F = kt^2 acts on b

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4-2.Friction

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A block of mass $4\,kg$ is placed on a rough horizontal plane A time dependent force $F = kt^2$ acts on the block, where $k = 2\,N/s^2$. Coefficient of friction $\mu = 0.8$. Force of friction between block and the plane at $t = 2\,s$ is ....... $N$

A

$8$

B

$4$

C

$2$

D

$32$

Solution

$\mathrm{F}_{\mathrm{max}}=\mu \mathrm{mg}=32 \mathrm{N}$

$F(t=2)=8 N$

as $\mathrm{F}<\mathrm{F}_{\max } \Rightarrow$ friction $=8 \mathrm{N}$

Standard 11

Physics

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