For the given figure, if block remains in equilibrium position then find frictional force between block and wall ........ $N$ 

An isolated rail car originally moving with speed $v_0$ on a straight, frictionles, level track contains a large amount of sand. $A$ release valve on the bottom of the car malfunctions, and sand begins to pour out straight down relative to the rail car. What happens to the speed of the rail car as the sand pours out? 

When a body slides down from rest along a smooth inclined plane making an angle of $45^o$ with the horizontal, it takes time $T$. When the same body slides down from rest along a rough inclined plane making the same angle and through the same distance, it is seen to take time $pT$, where $p$ is some number greater than $1$. Calculate the coefficient of friction between the body and the rough plane.

Imagine the situation in which the given arrangement is placed inside a trolley that can move only in the horizontal direction, as shown in figure. If the trolley is accelerated horizontally along the positive $x$ -axis with $a_0$, then Identify the correct statement $(s)$ related to the tension $T$ in the string

What is the maximum value of the force $F$ such that the block shown in the arrangement does not move ....... $N$

A circular racetrack of radius $300\; m$ is banked at an angle of $15^o$. If the coefficient of friction between the wheels of a race-car and the road is $0.2$, what is the

$(a)$ optimum speed of the racecar to avoid wear and tear on its tyres, and

$(b)$ maximum permissible speed to avoid slipping ?