# Physics 1st Paper CQ-Cumilla Board-2021

প্রশ্ন ·সময় ২ ঘণ্টা ৩৫ মিনিট

1. In figure, $\overrightarrow{F_{1}}$ and $\overrightarrow{F_{2}}$ forces are acting at point $O$.

CB 21
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

2. In place 'P' due to the excessive cool the time of a second pendulumis changed in such a way that, it goes $15 \mathrm{sec}$ fast per day. Then this pendulum is brought in another place ' $\mathrm{N}$ ' at the same temperature. Theacceleration due to gravity is decreased by $5 \%$ in place ' $\mathrm{N}$ ' then the place ' $\mathrm{P}$ '. $\left[\mathrm{g}=9.8 \mathrm{~ms}^{-2}\right]$

CB 21
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

3. To measure the depth of a lake of saline water, a diver takes a balloon filled with one mole of helium gas of volume $2.5 \times 10^{-2} \mathrm{~m}^{3}$ at pressure $1.013 \times 10^{5} \mathrm{Nm}^{-1}$ to the bottom from the lake surface and finds that the volume decreases to half of its initial volume. At this the diver remarks that the depth of the lake is $9 \mathrm{~m}$. It is mentioned that the temperature of gas and lake water is same. [Density of lake water $1.1 \times 10^{3} \mathrm{kgm}^{-3}, \mathrm{~g}=9.8 \mathrm{~ms}^{-2}, \mathrm{R}$ $=8.314 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$, Air pressure at the lake surface $=$ $\left.1.013 \times 10^{5} \mathrm{Nm}^{-2}\right]$

CB 21
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

4. A car of mass $1400 \mathrm{~kg}$ is taking turn on a road of $20 \mathrm{~m}$ width. The outer end of the road is $0.75 \mathrm{~m}$ higher than the inner end. Radius of the track is $100 \mathrm{~m}$. The passengers request the driver to drive the car at the velocity $8 \mathrm{~ms}^{-1}$.

CB 21
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

5. A wheel of $5 \mathrm{~kg}$ mass and $30 \mathrm{~cm}$ radius rotates 60 times per minute. A $0.45 \mathrm{~N}-\mathrm{m}$ torque is applied to wheel to stop within 5 seconds.

CB 21
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো