Match the following physical quantities in $LIST$-$I$ with their dimensional formulas in $LIST$-$II$:

$LIST$-$I$	$LIST$-$II$
$A$. Planck's constant	$I$. $ML^2T^{-2}$
$B$. Stopping potential	$II$. $T^{-1}$
$C$. Work function	$III$. $ML^2T^{-1}$
$D$. Threshold frequency	$IV$. $ML^2T^{-3}A^{-1}$

Identify the pair whose dimensions are equal.

Match the entries in List-$I$ with those in List-$II$.

$A$. Unified interaction reducing the number of fundamental forces from four to three	$(i)$ Strong interaction
$B$. Force between two molecules separated by a distance near about the sum of the molecular radii	$(ii)$ Gravitational force
$C$. Nuclear binding force	$(iii)$ Electroweak interaction
$D$. Bodies of astronomical proportions	$(iv)$ Electromagnetic interaction

Which of the following groups has different dimensions?

Choose the correct match:

List-$I$	List-$II$
$(i)$ Curie	$(A)$ $MLT^{-2}$
$(ii)$ Light year	$(B)$ $M$
$(iii)$ Dielectric strength	$(C)$ Dimensionless
$(iv)$ Atomic weight	$(D)$ $T$
$(v)$ Decibel	$(E)$ $ML^2T^{-2}$
	$(F)$ $MT^{-3}$
	$(G)$ $T^{-1}$
	$(H)$ $L$
	$(I)$ $MLT^{-3}I^{-1}$
	$(J)$ $LT^{-1}$

Just as precise measurements are necessary in science,it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain,try to get an upper bound on the quantity):
$(a)$ The total mass of rain-bearing clouds over India during the Monsoon.
$(b)$ The mass of an elephant.
$(c)$ The wind speed during a storm.
$(d)$ The number of strands of hair on your head.
$(e)$ The number of air molecules in your classroom.