Which of the following is known as the pitcher plant?

$A$ closed pipe is suddenly opened and changed to an open pipe of the same length. The fundamental frequency of the resulting open pipe is less than that of the $3^{rd}$ harmonic of the earlier closed pipe by $55 ~Hz$. Then,the value of the fundamental frequency of the closed pipe is: (in $~Hz$)

In the circuit shown in the figure,the $AC$ source gives a voltage $V = 20 \cos(2000t)$. Neglecting source resistance,the voltmeter and ammeter readings will be

During which time interval is the particle described by these position graphs at rest?

Which of the following statements are true about acceleration due to gravity?
$(a)$ $g$ decreases in moving away from the centre if $r > R$
$(b)$ $g$ decreases in moving away from the centre if $r < R$
$(c)$ $g$ is zero at the centre of the Earth
$(d)$ $g$ decreases if the Earth stops rotating on its axis

$A$ mass $M$ hangs on a massless rod of length $l$ which rotates at a constant angular frequency. The mass $M$ moves with steady speed in a circular path of constant radius. Assume that the system is in steady circular motion with constant angular velocity $\omega$. The angular momentum of $M$ about point $A$ is $L_A$ which lies in the positive $z$ direction and the angular momentum of $M$ about $B$ is $L_B$. The correct statement for this system is