$A$ car is moving on a plane inclined at $30^{\circ}$ to the horizontal with an acceleration of $10 \, ms^{-2}$ parallel to the plane upward. $A$ bob is suspended by a string from the roof of the car. The angle in degrees which the string makes with the vertical is ...... . (Take $g = 10 \, ms^{-2}$)

$A$ perfectly smooth sphere $A$ of mass $2 \ kg$ is in contact with a rectangular block $B$ of mass $4 \ kg$ and a vertical wall as shown in the figure. All surfaces are smooth. Find the normal reaction exerted by the vertical wall on sphere $A$ (in $N$). Take $g = 10 \ m/s^2$.

$A$ block of mass $m$ is released on a smooth inclined plane of inclination $\theta$ with the horizontal. The force exerted by the plane on the block has a magnitude

$A$ block of mass $m_1 = 2\,kg$ on a smooth inclined plane at an angle of $30^\circ$ is connected to a second block of mass $m_2 = 3\,kg$ by a cord passing over a frictionless pulley as shown in the figure. The acceleration of each block is ....... $m/s^2$ (assume $g = 10\,m/s^2$).

Block $A$ of weight $100 \, N$ rests on a frictionless inclined plane of slope angle $30^{\circ}$. $A$ flexible cord attached to $A$ passes over a frictionless pulley and is connected to block $B$ of weight $w$. Find the weight $w$ for which the system is in equilibrium.

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 $= 10 \ m \ s^{-2}$)