In the figure shown,$A$ and $B$ are free to move. All the surfaces are smooth. Then for $(0 < \theta < 90^o)$:

$A$ 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?

$A$ body starts falling freely from height $H$ and hits an inclined plane in its path at height $h$ from the ground. As a result of this perfectly elastic impact,the direction of the velocity of the body becomes horizontal. The value of $\frac{H}{h}$ for which the body will take the maximum time to reach the ground is . . . . . . .

$A$ 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 $g = 10 \, ms^{-2}$)

$A$ solid sphere,a hollow sphere,and a ring are released from the top of a frictionless inclined plane,causing them to slide down the plane. For which object is the acceleration down the plane the maximum?

$A$ football of radius $R$ is kept on a hole of radius $r$ (where the diameter of the hole is $2r$ and $r < R$) made on a plank kept horizontally. One end of the plank is now lifted so that it gets tilted,making an angle $\theta$ with the horizontal as shown in the figure. The maximum value of $\theta$ such that the football does not start rolling down the plank satisfies (figure is schematic and not drawn to scale) -