The maximum and minimum melting points of the first and second transition series elements,respectively,are obtained with:

What is the primary objective of plant breeding?

$A$ ball is let fall from a height $h_0$. It makes $n$ collisions with the earth. After $n$ collisions it rebounds with a velocity $v_n$ and the ball rises to a height $h_n$. Then the coefficient of restitution is given by:

The decreasing order of nucleophilicity among the following nucleophiles is:
$(I)$ $CH_3-COO^-$
$(II)$ $CH_3-O^-$
$(III)$ $CH_3-CH_2^-$
$(IV)$ $CH_3-SO_3^-$

$DDT$ residues are rapidly passed through food chains causing biomagnification. What is the reason for this?

Two particles $P$ and $Q$ start from the origin and execute simple harmonic motion along the $X$-axis with the same amplitude but with periods $3 \ s$ and $6 \ s$,respectively. The ratio of the velocities of $P$ and $Q$ when they meet is