When two surfaces are coated with a lubricant, then they

A block of mass $50 \,kg$ can slide on a rough horizontal surface. The coefficient of friction between the block and the surface is $0.6$. The least force of pull acting at an angle of $30^°$ to the upward drawn vertical which causes the block to just slide is ........ $N$

An army vehicle of mass $1000\, kg$ is moving with a velocity of $10 \,m/s$ and is acted upon by a forward force of $1000\, N$ due to the engine and a retarding force of $500 \,N$ due to friction. ........... $m/s$ will be its velocity after $10\, s$

As shown in the figure a block of mass $10\,kg$ lying on a horizontal surface is pulled by a force $F$ acting at an angle $30^{\circ}$, with horizontal. For $\mu_{ s }=0.25$, the block will just start to move for the value of $F..........\,N$ : $\left[\right.$ Given $\left.g =10\,ms ^{-2}\right]$

A truck starting from rest moves with an acceleration of $5 m/s^2$ for $1 sec$ and then moves with constant velocity. The velocity $w.r.t$ ground $v/s$ time graph for block in truck is ( Assume that block does not fall off the truck)

In the figure, a ladder of mass $m$ is shown leaning against a wall. It is in static equilibrium making an angle $\theta$ with the horizontal floor. The coefficient of friction between the wall and the ladder is $\mu_1$ and that between the floor and the ladder is $\mu_2$. The normal reaction of the wall on the ladder is $N_1$ and that of the floor is $N_2$. If the ladder is about to slip, then

$Image$

$(A)$ $\mu_1=0 \mu_2 \neq 0$ and $N _2 \tan \theta=\frac{ mg }{2}$

$(B)$ $\mu_1 \neq 0 \mu_2=0$ and $N_1 \tan \theta=\frac{m g}{2}$

$(C)$ $\mu_1 \neq 0 \mu_2 \neq 0$ and $N _2 \tan \theta=\frac{ mg }{1+\mu_1 \mu_2}$

$(D)$ $\mu_1=0 \mu_2 \neq 0$ and $N _1 \tan \theta=\frac{ mg }{2}$