## IIT JEE Physics Test Paper 3

** IIT JEE Physics Test Paper 3 **

** Part – I (Physics)**

This section contains 30 multiple choice questions. Each questions has 4 choices (A), (B), (C) and (D) out of which only one is correct.

**1. A wall is moving constant velocity u towards a fixed source of sound of frequency ‘f’. the velocity of sound is ‘v’. The wavelength of the sound reflected by the wall is**

(A) v-u/f (B) v+u/f (C) (v-u/v+u) /(v /f) (D)(v+u/v-u) /(v /f)

**2. A tube of length l open at only one end is cut into two equal halves. the sixth overtone frequency of piece closed at one end equals to sixth overtone frequency of piece open at both ends. The radius of cross-secton of tube is:**

(A) 5l/72 (B) l/24 (C) 5l/24 (D) 5l/12

**3. Propagation of a sound wave in a gas is quite close to:**

(A) an isothermal process (B) an adiabatic process

(C) an isobaric process (D) None of these

**4. Figure shown in a graph, at a certain time t, of the displacement**

function S(x, t) of three sound waves 1,2 and 3 as marked on the

curves that travel along x–axis through air. If P1, P2 and P3 repre-sent their pressure amplitudes respectively, then correct relation between them is:

(A) P1 > P2 > P3 (B) P3 > P2 > P1 (C) P1 = P2 = P3 (D) P1 > P2 = P3

**5. The velocity of sound in a gas is 360 m/s and the distance between a compression and the nearest rarefac-tion is 1m, then the frequency of sound will be:**

(A) 360 Hz (B) 90 Hz (C) 180 Hz (D) 120 Hz

**6. A string of length ‘l’ is fixed at both ends. It is vibrating in its 3rd overtone with maximum amplitude ‘a’. The ****amplitude at a distance 3 from one end is:**

(A) a (B) 0 (C) sqrt(3)a/2 (D) a/2

** 7. A pressure P and absolute temperature T a mass M of an ideal gas fills a closed container of volume V. An ****V additional mass 2M of the same gas is added into the container and the volume is then reduced to V/3 and the temperature to T/3. The pressure of the gas will now be:**

(A) P (B) 3 P (C) 9 P (D) 8 P

**8. A string of length L, fixed at its both ends is vibrating in its 1st overtone mode. Consider two elements of the string of same small length at positions L1= 0.2 L and L2= 0.45 L from one end. If K1 and K2 are their respective maximum kinetic energies then **

(A) K1 = K2 (B) K1 > K2

(C) K1 < K2 (D) it is not possible to decide the relation

**9. In the figure (i) an extensible string is fixed at one end and the other end is pulled by a tension**

** T. In figure (ii) another identical string is pulled by tenstion ‘T’ at both the ends. The ratio of**

**elongation in equilibrium of string in (i) to the elongation of string in (ii) is**

(A) 1 : 1 (B) 1 : 2 (C) 2 : 1 (D) 4 : 1

**10. The velocity of sound in a gas at temperature 27ºC is V then in the same gas its velocity will be 2V at temperature:**

(A) 54ºC (B) 327ºC (C) 927ºC (D) 108ºC

**A wave represented by equation y = 2(mm) sin[4pi (sec–1)t – 2pi(m–1)x] is superimposed with another wave y = 2(mm) sin[4pi(sec–1]t + 2pi(m–1)x + pi/3] on a tight string (Neglecting dissipative losses answer the following) :**

**11. Phase difference between two particles which are located at x 1 = 1/7 m and x 2 = 5 /12 m is:**

(A) 0 (B)5pi/6 (C) pi (D)5pi/3

**12. Which of the following is not a location of antinode:**

(A) 5/12 m (b) 11/12 m (c) 2/3 m (d) 17/12 m

**Paragraph-02 (Questions : 13 to 14)**

**A point source of sound ‘S’ generating sound of 875 Hz is moving along straight line with speed 50 m/s as shown in figure. A stationary observer ‘O’ is situated at a perpendicular distance 300 m from CD as**

** shown. Speed of sound is 300 m/s. Based on given information answer the following:**

**13. Calculate frequency of sound observed by observer when source is at point A:**

(A) 900 Hz (B) 899 Hz (C) 875 Hz (D) 600 Hz

14. Distance between observer and source when observer hears original frequency:

(A) 300 m (B) 305 m (C) 50 sqrt(37) m (D) None of these

**Consider a situation as shown in figure in which a rope of mass ‘m’ and length ‘l’ is attached to fixed celling. Other**

** end is free. Free end is given a small disturbance and this**

**disturbance travels in upwards direction.**

**15. The velocity of disturbance when it is at a height ‘x’ from bottom end is:**

(A)sqrt(2xg) (B)sqrt(g/l) (c) sqrt(gl) (d)sqrt(xg)

**16. Acceleration of disturbance is:**

(A) zero (B) g (C) g/2 (D) 2g

**17. An uncharged sphere of metal placed a charged parallel plate capacitor. The lines of force look like**

**18. Potential difference between centre & the surface of sphere of radius R and uniform volume charge density rho within it will be:**

(A)rho R^2/6E0 (B)rho R^2/4E0 (c) 0 (d)rho R^2/2E0

**19. If the electric potential of the inner metal sphere is 10 volt & that of the outer shell is 5 volt, then the potential at the centre will be:**

(B) 5 volt

(C) 15 volt

(D) 0

**20. An infinite number of concentric rings carry a charge Q each al-ternately positive and negative. Their radii are 1,2,4,8………meters in geometric progression as shown in the figure. The potential at the center of the rigs will be**

(A) Zero (b) Q/12piE0 (c)Q/8piE0 (d) Q/6piE0

**21. When a negative charge is released and moves in electric field, it moves toward a position of**

(A) lower electric potential and lower potential energy

(B) lower electric potential and higher potential energy

(C) higher electric potential and lower potential energy

(D) higher electric potential and higher potential energy

**22. Two particles X and Y, of equal mass and with unequal positive charges, are free to move and are initially far away from each other. With Y at rest, X begins to move towards it with initial velocity u. after a long time, finally**

(A) X will stop, Y will move with velocity u. (B) X and Y will both move with velocities u/2 each.

(C) X will stop, Y will move with velocity < u. (D) both will move with velocities < u/2

**23. A circular ring of radius R with uniform positive charge charge density lamda per unit length is located in the y-z plane with its centre at the origin O. A particle of mass m and positive charge q is projected from the point P(Rsqrt( 3),O,O) on the positive X-axis directly towards O, with an initial kinetic energy lamda(q)/4E0 .**

(A) The particle crosses O and goes to infinity (B) The particle returns to P.

(C) The particle will just reach O (D) The particle crosses O and goes to -Rsqrt(3)

**24. A bullet of mass m and charge q is fired towards a solid uniformly charged sphere of radius R and total charge +q. If it strikes the surface of sphere with speed u, find the minimum speed u so that it can penetrate through the sphere. (Neglect all resistance forces or friction acting on bullet except electrostatic forces)**

(A)q/sqrt(2piE0mR) (B)q/sqrt(4piE0mR) (c)q/sqrt(8piE0mR) (d)sqrt(3)q/sqrt(4piE0mR)

**25. Two identical particles of mass m carry a charge Q each. Initially one is at rest on a smooth horizontal plane and the other is projected along the plane directly towards first particle from a large distance with speed v . The closed distance of approach be**

(A)(1/ 4piE0).(Q^2/mv) (b)(1/ 4piE0).(Q^2/mv)

**26. The equation of an equipotential line in an electric field y = 2x, then the electric field strength vector at (1, 2) may be**

(A) 4ˆi + 3ˆj (B) 4ˆi + 8ˆj (C) 8ˆi +4ˆj (D) -8ˆi + 4ˆj

** 27. A charge 3 coulomb experiences a force 3000 N when placed in a uniform electric field. The potential ****difference between two points separated by a distance of 1 cm along the field lines is**

(A) 10 V (B) 90 V (C) 1000 V (D) 9000 V

**28. A uniform electric field having strength E is existing in x-y plane as shown in figure. Find the p.d. between origin O & A (d, d, 0)**

29. A, B, C, D, P and Q are points in a uniform electric field. The potentials a these points are V (A) = 2

volt. V (P) = V (D) = 5 volt. V (C) = 8 volt. The electric field at P is

(A) 10 Vm–1 along PQ

(B) 15 sqrt(2) V /m along PA

(C) 5 V /m along PC

(D) 5 V /m along PA

**30. Figure shows the electric field lines around an electric dipole. Which of the arrows best repre-**

** sents the electric field at point P ?**