A block of mass $2\,kg$ moving on a horizontal surface with speed of $4\,ms ^{-1}$ enters a rough surface ranging from $x =0.5\,m$ to $x =1.5\,m$. The retarding force in this range of rough surface is related to distance by $F =- kx$ where $k =12\,Nm ^{-1}$. The speed of the block as it just crosses the rough surface will be ........... $\,ms ^{-1}$
A$0$
B$1.5$
C$2.0$
D$2.5$
JEE MAIN 2022, Diffcult
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C$2.0$
c $a=\frac{- kx }{2}=\frac{-12 x }{2}=-6 x$
$\frac{ v d v }{ dx }=-6 x$
$\int \limits_{4}^{*} vdv =-\int \limits_{\frac{1}{2}}^{ s / 2} 6 xdx$
$\frac{ v ^{2}-4^{2}}{2}=-\frac{6}{2}\left[\left(\frac{3}{2}\right)^{2}-\left(\frac{1}{2}\right)^{2}\right]$
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A force $F = Kt$ (where $t$ is the time in seconds and $K = 2\, N/s$) is applied on $2 \,kg$ block at $t = 0$ as shown in the figure. The displacement of $8\ kg$ block till the time when $2\, kg$ block start slipping on $8\,kg$ block will be (coefficient of friction between $2\,kg$ block and $8\, kg$ block is $0.2$ and between $8\, kg$ block and surface is zero,
$g = 10m/s^2)$
A block of mass $m$ is moving with a constant acceleration a on a rough plane. If the coefficient of friction between the block and ground is $\mu $, the power delivered by the external agent after a time $t$ from the beginning is equal to
A body of mass $2$ kg is moving on the ground comes to rest after some time. The coefficient of kinetic friction between the body and the ground is $0.2$. The retardation in the body is ...... $m/s^2$
A body of mass $2\,kg$ slides down with an acceleration of $3\,m/s^2$ on a rough inclined plane having a slope of $30^o$ . The external force required to take the same body up the plane with the same acceleration will be $... N$ $(g\, = 10\, m/s^2)$
A block of mass $0.1 \,kg$ is held against a wall by applying a horizontal force of $5\, N$ on the block. If the coefficient of friction between the block and the wall is $0.5$, the magnitude of the frictional force acting on the block is ........ $N$
A block of mass $10\, kg$ is placed on a rough horizontal surface having coefficient of friction $\,\mu = 0.5$. If a horizontal force of $100\, N$ is acting on it, then acceleration of the block will be ....... $m/s^2$
Given in the figure are two blocks $A$ and $B$ of weight $20\ N$ and $100\ N,$ respectively. These are being pressed against a wall by a force $F$ as shown. If the coefficient of friction between the blocks is $0.1$ and between block $B$ and the wall is $0.15$, the frictional force applied by the wall on block $B$ is ........... $N$
A uniform wooden stick of mass $1.6 \mathrm{~kg}$ and length $l$ rests in an inclined manner on a smooth, vertical wall of height $h( < l)$ such that a small portion of the stick extends beyond the wall. The reaction force of the wall on the stick is perpendicular to the stick. The stick makes an angle of $30^{\circ}$ with the wall and the bottom of the stick is on a rough focr. The reaction of the wall on the stick is equal in magnitude to the reaction of the floor on the st $ck$. The ratio $h / l$ and the frictional force $f$ at the bottom of the stick are $\left(g=10 \mathrm{~m} \mathrm{~s}^{-2}\right)$