Physics 1st Paper CQ-Dinajpur Board-2017

1. Ten water droplets of same shapes formed big droplets. The diameter of each small droplets is $5 \times 10^{-7} \mathrm{~m}$. The surface tension of water is $72 \times 10^{-3} \mathrm{Nm}^{-1}$.

2. The volume of a gas cylinder is $1.5 \mathrm{~m}^{3}$. There are $30 \times 10^{25}$ molecules in the cylinder at $27^{\circ} \mathrm{C}$ temperature. Later on, the cylinder was attached to another bare cylinder of the same volume.

3. Noyon is moving a $25 \mathrm{~g}$ stone with a $1 \mathrm{~m}$ long wire in a circular shape. The stone is moving 5 times per second. The length of wire is increased by two times and the number of rotations remains the same. The wire can tolerate $40 \mathrm{~N}$ force.

4. Two tuning fork A and B create a sound of wave length $50 \mathrm{~cm}$ and $51 \mathrm{~cm}$ in a gas. If both the tuning forks are tuned at the same time 6 beats are heard per second. The frequency of $\mathrm{A}$ is $500 \mathrm{~Hz}$

5. The radius and mass of a cosmological object is $3.2 \times 10^{6} \mathrm{~m}$ and $4 \times 10^{24} \mathrm{~kg}$ respectively. Gravitational constant, $G=$ $6.675 \times 10^{-11} \mathrm{Nm}^{2} \mathrm{~kg}^{-2}$. The object was divided into 8 parts due to the hit from a comet.