$A$ body takes $4 \, s$ to reach the bottom of an inclined plane from the top. How much time (in $s$) will it take to cover one-fourth of the distance?

$A$ block slides down a smooth inclined plane when released from the top,while another falls freely from the same point. Which of the following statements is correct?

Two masses $M_1$ and $M_2$ are attached to the ends of a light string which passes over a massless pulley attached to the top of a double inclined smooth plane of angles of inclination $\alpha$ and $\beta$. The tension in the string is:

Two masses $M_1$ and $M_2$ are arranged as shown in the figure. Let '$a$' be the magnitude of the acceleration of the system. If the mass of $M_1$ is doubled and that of $M_2$ is halved,then the new acceleration of the system is (Treat all surfaces as smooth; masses of pulley and rope are negligible).

As shown in the figure,an iron block $A$ of volume $0.25 \ m^3$ is attached to a spring $S$ of unstretched length $1.0 \ m$ and hanging from the ceiling. The spring gets stretched by $0.2 \ m$. This block is removed and another iron block $B$ of volume $0.75 \ m^3$ is now attached to the same spring and kept on a frictionless inclined plane of $30^{\circ}$ inclination. The distance of the block from the top along the incline at equilibrium is (in $m$)

Two smooth inclined planes $A$ and $B$ each of height $20 \ m$ have angles of inclination $30^{\circ}$ and $60^{\circ}$ respectively. If $t_1$ and $t_2$ are respectively the times taken by two blocks to reach the bottom of the planes $A$ and $B$ from the top,then $t_1 - t_2 = $ (Acceleration due to gravity $= 10 \ m \ s^{-2}$)