Someone is using a scissors to cut a wire of circular cross section and negligible weight. The wire slides in the direction away from the hinge until the angle between the scissors blades becomes $2 \alpha$. The friction coefficient between the blades and the wire, is :-
$\sqrt {1-tan \alpha}$
$2cos \alpha$
$tan \alpha$
$2\, tan \alpha$
A block weighs $W$ is held against a vertical wall by applying a horizontal force $F$. The minimum value of $F$ needed to hold the block is
A block of wood resting on an inclined plane of angle $30^o$, just starts moving down. If the coefficient of friction is $0.2$, its velocity (in $ms^{-1}$) after $5\, seconds$ is : $(g = 10\, ms^{-2})$
A block of $1\, kg$ is stopped against a wall by applying a force $F$ perpendicular to the wall. If $\mu = 0.2$ then minimum value of $F$ will be ....... $N.$
A block of $7\,kg$ is placed on a rough horizontal surface and is pulled through a variable force $F$ (in $N$ ) $= 5\,t$ , where $'t'$ is time in second, at an angle of $37^o$ with the horizontal as shown in figure. The coefficient of static friction of the block with the surface is one. If the force starts acting at $t = 0\,s$ . Find the time at which the block starts to slide ......... $\sec$ (Take $g = 10\,m/s^2$ )
A block pressed against the vertical wall is in equilibrium. The minimum coefficient of friction is:-