The distance of a galaxy is of the order of $10^{25} \ m$. Calculate the order of magnitude of time taken by light to reach us from the galaxy.

Which of the following quantities has a unit but is dimensionless?

Match the following?

Column-$I$	Column-$II$
$(a)$ Ratio of change in time period of a simple pendulum with temperature to its original time period	$(i) \, \alpha \Delta T$
$(b)$ Ratio of the value of a length to its scale reading	$(ii) \, T$
$(c)$ Reciprocal of coefficient of volume expansion for an ideal gas of constant pressure	$(iii) \, (1 + \alpha \Delta T)$
$(d) \, \frac{F}{YA} =$	$(iv) \, \frac{1}{2} \alpha \Delta T$

Which of the following pairs of physical quantities have the same dimensions,where one is a vector and the other is a scalar?

Fill in the blanks:
$(a)$ To measure the direct distance of a mountain,....... is used.
$(b)$ For the measurement of time,the ........... clock is the most accurate.
$(c)$ Rounding off $15.753$ to three significant figures gives ....... .

Match List-$I$ with List-$II$:

$LIST$-$I$	$LIST$-$II$
$(A)$ Surface tension	$(I)$ $kg m^{-1} s^{-1}$
$(B)$ Pressure	$(II)$ $kg m s^{-1}$
$(C)$ Viscosity	$(III)$ $kg m^{-1} s^{-2}$
$(D)$ Impulse	$(IV)$ $kg s^{-2}$

Choose the correct answer from the options given below: