A body of mass m rests on horizontal surface. The coefficient of friction between the body and the surface is $\mu .$ If the mass is pulled by a force $P$ as shown in the figure, the limiting friction between body and surface will be
$\mu mg$
$\mu \,\left[ {mg + \left( {\frac{P}{2}} \right)} \right]$
$\mu \,\left[ {mg - \left( {\frac{P}{2}} \right)} \right]$
$\mu \,\left[ {mg - \left( {\frac{{\sqrt 3 \,P}}{2}} \right)} \right]$
A boy of mass $4\, kg$ is standing on a piece of wood having mass $5 \,kg$. If the coefficient of friction between the wood and the floor is $0.5,$ the maximum force that the boy can exert on the rope so that the piece of wood does not move from its place is ......$N.$(Round off to the Nearest Integer) [Take $g=10 \,ms ^{-2}$ ]
A block of mass $10\, kg$ moving at $10\,m/s$ is released to slide on rough surface having coefficient of friction $0.2.$ It will stop by travelling distance ........ $m$
A chain of length $L$ rests on a rough table. If $\mu $ be the coefficient of friction, the maximum friction of the chain that can hang over the table will be
Which one of the following is not used to reduce friction
Aball of mass $m$ is thrown vertically upwards.Assume the force of air resistance has magnitude proportional to the velocity, and direction opposite to the velocity's. At the highest point, the ball's acceleration is