Tension

Q. The length of a sonometer wire is $0.75\text{m}$ and density is $9\times {10}^3{\text{kg/m}}^3$. It can bear a stress of $8.1\times {10}^8{\text{N/m}}^2$ without exceeding elastic limit. The fundamental frequency that can be produced in the wire is

1. $175\text{Hz}$
2. $200\text{Hz}$
3. $150\text{Hz}$
4. $225\text{Hz}$

Q. A copper wire is held at the two ends by rigid supports. At ${30}^{\circ }C$ the wire is just taut, with negligible tension. The speed of a transverse wave in this wire at ${10}^{\circ }C$ is $x\text{m/s}$. The value of $x$ is [Give your answer as nearest integer value]

[Given Young modulus of copper$=1.3\times {10}^{11}{\text{N/m}}^2$,
Co-efficient of linear expansion of copper $=1.7\times {10}^{-5}{}^{\circ }{C}^{-1}$,
Density of copper $=9\times {10}^3{\text{kg/m}}^3$]

Q. Why tension is an Electromagnetic force ?

Q. A steel wire is rigidly fixed at both ends. Its length, mass and cross-sectional area are $1\text{m, 0.1 kg and}{10}^{-6}{\text{m}}^2$respectively. Tension in the wire is produced by lowering the temperature by ${20}^{\circ }\text{C}$. If transverse waves are set up by plucking the wire at $0.25\text{m}$ from one end, and assuming that the wire vibrates with minimum number of loops possible for such a case. The frequency of vibration (in $Hz$) is found to be $11\times \text{K}$. Find the value of $K$.$(\text{Given}\alpha =1.21\times {10}^{-5\circ }{C}^{-1},Y=2\times {10}^{11}N/m^2)$

1. $2$
2. $4$
3. $11$
4. $22$

Q. A string of length $1m$ fixed at both ends is vibrating in $3^{rd}$ overtone. Tension in string is $200N$ and linear mass denstiy is $5gm/m$. Frequency of these vibrations is (in $Hz$).

Q. A sonometer wire of length $1.5\text{m}$ is made of steel. The tension in it produces an elastic strain of $1\%$. What is the fundamental frequency of steel, if density and elasticity of steel are $7.7\times {10}^3{\text{kg/m}}^3$ and $2.2\times {10}^{11}{\text{N/m}}^2,$ respectively?

Q. An organ of length $L$ is open at one end closed at other end. The air column in the pipe is vibrating in second overtone. The minimum distance from the open end where the pressure amplitude is half of the maximum value is

1. $L/4$
2. $L/8$
3. $L/12$
4. $L/15$

Q. Why is tension in a string electromagnetic force?

Q. In a sonometer wire the tension is maintained by suspending a $50.7kg$ mass from the free end of the wire. The suspended mass has a volume of $0.0075m^3$. The fundamental frequency of the wire is $260Hz$. Find the new fundamental frequency (in Hz) if the suspended mass is completely submerged in water.

Q. Two stretched wires of same length, diameter and same material are in unison. The tension in one is increased by $2\%$ and $2$ beats per second are heard. What was the frequency of the note produced when they were in unison

1. $100Hz$
2. $200Hz$
3. $500Hz$
4. $400Hz$

Q. Consider the situation shown in figure. A horizontal disc of mass m, radius R suspended from the centre through a wire of torsional rigidity k.If at $t=0$, the disc is deviated by ${\varphi }_0$, find the energy of small torsional vibrations:

1. $\frac{1}{4}k{\varphi }_0^2$
2. $\frac{1}{2}k{\varphi }_0^2$
3. $k{\varphi }_0^2$
4. $2k{\varphi }_0^2$

Q. Two blocks of mass m and M are hanging off a single pulley, as shown. Determine the acceleration of the blocks. Ignore the mass of the pulley. m = 1 kg and M = 2 kg, g= 10 $m/s^2$.

1. 5/2
2. 10/3
3. 10
4. 10/7

Q. Fundamental frequency of an open organ pipe is in resonance with first overtone of a closed pipe. The ratio of their lengths is

1. 2:3
2. 3:2
3. 1:4
4. 4:1

Q.

In the movie gravity, astronauts Sandra Bullock & George Clooney are stranded in space and connected by a string. To come closer to each other they both start pulling the string from their ends. Assuming that if the astronauts are pulling the string with a force F then the tension in the string should be equal and in opposite direction and should pull the astronaut (According to Newton's 3rd law).

Then in that case the net force on each astronaut should be 0 and they shouldn't move according to 1st law. Why are the moving towards each other?

1. Obviously George Clooney will pull with a greater force and that's why they two will come closer.

2. The question is wrong. This can never happen. In movie they use jet packs to come closer.

3. They come closer because of gravitational attraction between them the string has nothing to do with this

4. None of these

Q. When two identical wires on a sonometer are kept under same tension, their fundamental frequency is $500Hz$. In order to produce five beats per second, the percentage change in the tension of one of the wires will be:

1. $2\text{\%}$
2. $4\text{\%}$
3. $6\text{\%}$
4. $8\text{\%}$

Q. A steel wire is rigidly fixed at both ends. Its length, mass and cross sectional area are $1m,0.1kg$ and ${10}^{-6}{m}^2$ respectively. Then the temperature of the wire is lowered by ${20}^{0}C.$ If the transverse waves are setup by plucking the wire at 0.25m from one end and assuming that wire vibrates with minimum number of loops possible for such a case.
[Coefficient of linear expansion of steel $=1.21\times {10}^{-5/0}C$ and Young's modulus $=2\times {10}^{11}N/m^2$]

1. The tension in the wire will be 48.4 N.
2. The number of loops will be 2.
3. The frequency of vibration will be 22 Hz.
4. The frequency of vibration will be 44 Hz.

Q. Can somebody explain inertial and non inertial frames? And also pseudo force.

Q.

The effect due to uniform magnetic field on a freely suspended magnetic needle will be?

1. both torque and net force an absent
2. net force is present but no torque
3. torque is present but no net force
4. both torque and net force are present

Q. 20.A mass m carrying a charge q is suspended from a string and placed in a uniform horizontal electric field of intensity E.The angle made by the string with the vertical in the equilibrium position is ---------

Q. A block pressed against the vertical wall is in equilibrium. The minimum coefficient of friction is

1. $0.4$
2. $0.2$
3. $0.5$
4. None of these

Q. A cylindrical tube open at both ends has a fundamental frequency $f$ in air. The tube is dipped vertically in water so that it has water up to the half height. The fundamental frequency of the air column is now
(Neglect end corrections)

1. $4f$
2. $3f$
3. $f$
4. $2f$

Q. A steel wire is rigidly fixed at both ends. Its length, mass and cross-sectional area are $1\text{m, 0.1 kg and}{10}^{-6}{\text{m}}^2$respectively. Tension in the wire is produced by lowering the temperature by ${20}^{\circ }\text{C}$. If transverse waves are set up by plucking the wire at $0.25\text{m}$ from one end, and assuming that the wire vibrates with minimum number of loops possible for such a case. The frequency of vibration (in $Hz$) is found to be $11\times \text{K}$. Find the value of $K$.$(\text{Given}\alpha =1.21\times {10}^{-5\circ }{C}^{-1},Y=2\times {10}^{11}N/m^2)$

1. $2$
2. $4$
3. $11$
4. $22$

Q. The length of a sonometer wire is $0.75m$ and density $9\times {10}^{3}k/m^3$It can bear a stress of $8.1\times {10}^{8}N/m^2$ with out exceeding the elastic limit The fundamental frequency that can be produced in the wire, is

1. $200Hz$
2. $150Hz$
3. $600Hz$
4. $450Hz$

Q. The length of a sonometer wire is $0.75\text{m}$ and density is $9\times {10}^3{\text{kg/m}}^3$. It can bear a stress of $8.1\times {10}^8{\text{N/m}}^2$ without exceeding elastic limit. The fundamental frequency that can be produced in the wire is

1. $200\text{Hz}$
2. $150\text{Hz}$
3. $175\text{Hz}$
4. $225\text{Hz}$