Physics 2nd Paper CQ-Mymensingh Board-2021

1. Observe the two circuits and answer the following questions:

2. An astronaut is going along the diameter of an imaginary planet with a velocity $1.8 \times 10^{\prime} \mathrm{ms}^{-1}$ to observe the density of the planet. The stationary mass of the planet is $7.4 \times 10^{25} \mathrm{~kg}$ and diameter is $14200 \mathrm{~km}$.

3. Jahed and Shahed are classmates. Jahed took resistance thermometer in Physics lab whose the resistances of ice point and boiling point are 120 and $24 \Omega$ respectively. On the other hand Shahed supplied $2400 \mathrm{~J}$ heat to a gas cylinder at 5 atm pressure. As a result the volume of the gas increases $1600 \mathrm{CF}^{\prime}$ to $3200 \mathrm{~cm}^{\prime}$ and the change of internal energy is 1589 AJ

4. In a Young's experiment through air medium, the wavelength of the used light is $5200 \Lambda$, the distance of the screen is $90 \mathrm{~cm}$ and separation between the two slite is $0.4 \mathrm{~mm}$. After that the experiment was done in glycerin and Kerosene medium. The refractive indices of glycerin and Kerosene are 1.47 and 1.44 respectively.

5. $A$ and $B$ are two engines. The engine- $A$ receives $2400 \mathrm{~J}$ heat at temperature $-60^{\circ} \mathrm{C}$ and rejects $3600 \mathrm{~J}$ heat to the heat sink of higher temperature. On the other hand, engine-B converts $5 \mathrm{~kg}$ of ice at $0^{\circ} \mathrm{C}$ into water of $0^{\circ} \mathrm{C}$ at the first stage and at the second stage converts $5 \mathrm{~kg}$ of water at $0^{\circ} \mathrm{C}$ into $100^{\circ} \mathrm{C}$. The latent heat of fusion of ice is $336000 \mathrm{Jkg}^{-1}$ and specific heat of water is 4200 $\mathrm{Jkg}^{-1} \mathrm{~K}^{-1}$.