Friction

Consider a car moving along a straight horizontal road with speed of $72 \mathrm{km} {\mathrm{hr}}^{-1}$  . If the coefficient of static friction between the tyres and the road is $0.5$, the shortest distance in which the car can be stopped is  (taking $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

The coefficient of static friction, ${\mu }_s,$  between block $A$ of mass $2 \mathrm{kg}$ and the table as shown in the figure is $0.2$. The maximum mass value of block $B$ so that the two blocks do not move is (The string and the pulley are assumed to be smooth and massless $g=10 \mathrm{m} {\mathrm{s}}^{-2})$

A block of mass $1 \mathrm{kg}$ is placed on a truck which accelerates with acceleration  $5 \mathrm{m} {\mathrm{s}}^{-2}$.  The coefficient of static friction between the block and truck is $\text{0.6}$. The frictional force acting on the block is

A block of mass $2 \mathrm{kg}$ rests on a rough inclined plane making an angle of $30º$ with the horizontal. The coefficient of static friction between the block and the plane is $0.7.$ The frictional force on the block is

A horizontal force of $10 \mathrm{N}$ is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is $0.2$. The weight of the block is –

A block of mass $1 \mathrm{kg}$ lies on a horizontal surface in a truck. The coefficient of static friction between the block and the surface is $0.6$. If the acceleration of the truck is $5\mathrm{m}{\mathrm{s}}^{-2}$. Find the frictional force acting on the block.

Friction force acting on object is given as function of angle '$\theta$' $f_r=\frac{\mu mg}{\sin \theta +\mu \cos \theta }$ then find $\theta$ where $f_r$ will be minimum.

A man walks over a rough surface, the angle between the force of friction and the instantaneous velocity of the person is:

A man walks over a rough surface starting from rest, the angle between the force of friction and the instantaneous velocity of the person is

Find the position coordinates of the image of the object $P$ as seen through the periscope. The mirrors are inclined at $45°$ with $x$-axis and eye is placed at the level $y=-d$.

A block is attached to a horizontal spring of stiffness $k$. The other end of the spring is attached to a fixed wall. The entire system lie on a horizontal surface and the spring is in natural state. The natural length of the spring is $l_0$. If the block is slowly lifted up vertically to a height $\frac{5}{12}{l}_0$  from its initial position. which of the following is not correct:

The kind of force that acts between moving surfaces is called _____.

$$\begin{gathered} \mathrm{A} \mathrm{raft} \mathrm{of} \mathrm{wood}( \mathrm{density} 600\mathrm{kg}/{\mathrm{m}}^3) \mathrm{of} \mathrm{mass} 120 \mathrm{kg} \mathrm{floats} \mathrm{in} \mathrm{water}. \mathrm{How} \mathrm{much} \mathrm{weight} \mathrm{can} \mathrm{be} \mathrm{put} \mathrm{on} \mathrm{the} \mathrm{raft} \mathrm{to} \mathrm{make} \mathrm{it} \\ "\mathrm{just} \mathrm{sink}" ? \end{gathered}$$

A body of mass $1kg$ moving on a horizontal surface with an initial velocity $6 m/s$ comes to rest after $3 seconds$. If one wants to keep the body moving on the same surface with the same velocity $6 m/s$, then the force required is

The buoyant force depends on the

A test tube containing some water is surrounded by melting ice (pure). Then, the water in the test tube will