If $\left|\begin{array}{ccc}\cos (A+B) & -\sin (A+B) & \cos 2 B \\ \sin A & \cos A & \sin B \\ -\cos A & \sin A & \cos B\end{array}\right|=0$,then $B$ is equal to

$A$ transverse wave is passing through a stretched string with a speed of $20 \ m/s$. The tension in the string is $20 \ N$. At a certain point $P$ on the string,it is observed that energy is being transferred at a rate of $40 \ mW$ at a given instant. Find the speed of point $P$.

The lines represented by the equation $x^2-y^2-x+3y-2=0$ are :

The number of sigma $(\sigma)$ bonds in $but-1-ene$ is:

$A$ force $F$ is applied on a square area of side $L$. If the percentage error in the measurement of $L$ is $2 \%$ and that in $F$ is $4 \%$,what is the maximum percentage error in pressure?

The figure shows the vertical section of a frictionless surface. $A$ block of mass $2 \, kg$ is released from position $A$. Its kinetic energy $(KE)$ as it reaches position $C$ is ............ $J$.