# Physics 1st Paper CQ-Jessore Board-2017

প্রশ্ন ·সময় ২ ঘণ্টা ৩৬ মিনিট

1. Mass of a simple pendulum's bob is $1.2 \times$ $10^{-2} \mathrm{~kg}$. It is swinging at an amplitude of $51 \mathrm{~mm}$. It takes $49.75 \mathrm{sec}$ to complete 25 oscillation. Radius of earth is 6.4 $\times 10^{6} \mathrm{~m}$.

JB 17
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

2. A student, keeping the pressure constant, increased the temperature of some $\mathrm{O}_{2}$ gas which was initially in ideal temperature. So, the volume doubled. And so his friend said that the mean square velocity of the molecules of experimented gas will be doubled too.

JB 17
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

3. A $30 \mathrm{gm}$ marble hit another stationary marble at $10 \mathrm{~ms}^{-1}$ velocity. After the collision, first marble lost its $75 \%$ velocity, the latter marble gained $9 \mathrm{~ms}^{-1}$ velocity and hit a clay wall at $3 \mathrm{~m}$ distance. The obstructing force of the wall is $3 \mathrm{~N}$. (Ignoring the air resistance)

JB 17
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

4. According to the picture, a boat is moving from position $A$ toward $A D$ of another side of a river, which has $2.5 \mathrm{~km}$ width.

Velocity of the boat on steady water $=(3 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}) \mathrm{m} \cdot \mathrm{s}^{-1}$ and velocity of tide $=2 \hat{i} \mathrm{~m} \cdot \mathrm{s}^{-1}$. In another case the boat is rowed along AB at the same speed.

JB 17
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো

5. A heavy $250 \mathrm{~N}$ symmetrical object $\mathrm{XY}$ is hanged from two equally long wires A and B horizontally. It is shown in the diagram (uncompressed state). Cross sectional area of each wire is $2.5 \times 10^{-7} \mathrm{~m}^{2}$. B wire's longitudinal strain is $2.5 \times 10^{-4} \mathrm{~m}^{2}$, A wire's $0.8 \mathrm{~m}$ is made of brass and the rest is steel.

Young's modulus for steel $=2 \times 10^{11} \mathrm{~Pa}$

Young's modulus for brass $=1 \times 10^{11} \mathrm{~Pa}$

JB 17
ব্যাখ্যা আনলক করতে চর্চা প্রিমিয়াম এ আপগ্রেড করো