A body is revolving with a constant speed along a circle. If its direction of motion is reversed but the speed remains the same, then, which of the following statements is true?

In the figure shown, calculate the angle of friction. The block does not slide. Take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$.

A block of mass $7 \mathrm{kg}$ is placed on a rough horizontal surface and is pulled through a variable force$F$ (in $\mathrm{N}$)$=5t$, where $t$ is time, in $\sec$, and makes an angle $37°$ with the horizontal, as shown in the figure. The coefficient of static friction of the block with the surface is $1$. If the force starts acting at $t=0 \sec$, find the time at which the block starts to slide (take $g$$=10 \mathrm{m} {\mathrm{s}}^{-2}$).

A block of mass $2 \mathrm{kg}$ is kept on the floor. The coefficient of static friction is$0.4$. If a force$F$ of $2.5$ $\mathrm{N}$ is applied on the block, as shown in the figure, the frictional force between the block and the floor will be

Two persons pull each other through a massless rope in a tug of war game. Who will win?

A rough vertical board has an acceleration $a$ so that a $2 \mathrm{kg}$ block pressing against it does not fall. The coefficient of friction between the block and the board should be

A bead of mass $m$ is located on a parabolic wire, with its axis vertical and vertex directed downward, as shown in the figure, and whose equation is $x^2=ay$. If the coefficient of friction is $\mu$, then the highest distance above the $x$-axis at which the particle will be in equilibrium is