An atomic power nuclear reactor can deliver $300\, MW$. The energy released due to fission of each nucleus of a uranium atom ${U^{238}}$ is $170\, MeV$. The number of uranium atoms fissioned per hour will be

An open pipe of length $33 \ cm$ resonates to a frequency of $1000 \ Hz$. The mode of vibration is: (velocity of sound $= 330 \ m/s$)

Two spheres $A$ and $B$ are kept very near to each other. $A$ is negatively charged and $B$ is earthed. The true statements are:
$(A)$ Charge on $B$ is zero
$(B)$ Potential at $B$ is zero
$(C)$ Charge is uniformly distributed on $A$
$(D)$ Charge is non-uniformly distributed on $A$

$2 \tanh^{-1} \frac{1}{2}$ is equal to

Two friends $A$ and $B$ are $30 \, km$ apart and they start simultaneously on motorcycles to meet each other. The speed of $A$ is $3$ times that of $B$. The distance between them decreases at the rate of $2 \, km$ per minute. Ten minutes after they start,$A$'s vehicle breaks down and $A$ stops and waits for $B$ to arrive. After how much time (in minutes) since $A$ started riding,does $B$ meet $A$?

The correct order of increasing ionic character is: