A particle of mass $m$ is at rest at the origin at time $t = 0$. It is subjected to a force $F(t) = F_0e^{-bt}$ in the $x$ -direction. Its speed $v(t)$ is depicted by which of  the  following curves ?

Pulling force making an angle $\theta $ to the horizontal is applied on a block of weight $W$ placed on a horizontal table. If the angle of friction is $\alpha $, then the magnitude of force required to move the body is equal to

A car is moving along a straight horizontal road with a speed ${v_0}$. If the coefficient of friction between the tyres and the road is $\mu $, the shortest distance in which the car can be stopped is

A heavy body of mass $25\, kg$ is to be dragged along a horizontal plane $\left( {\mu  = \frac{1}{{\sqrt 3 }}} \right).$ The least force required is ........ $kgf$ 

A block of mass $70\,kg$ is kept on a rough horizontal surface $(\mu = 0.4)$. A person is trying to pull the block by applying a horizontal force, but the block is not moving. The net contact force exerted by the surface on the block is $F$, then

What is friction ? What is impending motion ?