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NCERT Solutions for class 11 Physics | Chapter 14 - Oscillations

(1) For a magnet of a time period T magnetic moment is M. If the magnetic moment becomes one-fourth of the initial value, then the time period of oscillation becomes
[A] Half of the initial value
[B] tOne-fourth of the initial value
[C] Double of the initial value
[D] Four times the initial value
Answer: Double of the initial value
(2) The maximum velocity for a particle in S.H.M is 0.16 m/s and maximum acceleration is 0.64 m/s2 .The amplitude is
[A] 4 x 10-2 m
[B] 4 x 10-1 m
[C] 4 x 10 m
[D] 4 x 100 m
Answer: 4 x 10-2 m

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(3) A particle of mass m is hanging vertically by an ideal spring of force constant k. If the mass is made to oscillate vertically, its total energy is
[A] Maximum at extreme position
[B] Maximum at mean position
[C] Minimum at mean position
[D] Same at all positions
Answer: Same at all positions
(4) A simple pendulum on length l and mass m is suspended vertically. The string makes an angle θ with the vertical. The restoring force acting on the pendulum is
[A] mg tanθ
[B] mg sinθ
[C] – mg sinθ
[D] – mg cosθ
Answer: – mg sinθ
(5) A a place where g = 980 cm/sec2 the length of seconds pendulum is about
[A] 50 cm
[B] 100 cm
[C] 2 cm
[D] 2 m
Answer: 100 cm
(6) A particle executes S.H.M of amplitude A. At what distance from the mean position is its kinetic energy equal to its potential energy?
[A] 0.51 A
[B] 0.61 A
[C] 0.71 A
[D] 0.81 A
Answer: 0.71 A
(7) The time period of a simple pendulum is T remaining at rest inside a lift. Find the time period of the pendulum when the lift starts to move up with an acceleration of g/3
[A] T
[B] T/2
[C] 2T/5
[D] T√3/2
Answer: T√3/2
(8) The displacement of a particle performing simple harmonic motion is given by,x= 8 sin ωt + 6 cos ωt, where distance is in cm and time is in second. The amplitude of motion is
[A] 10 cm
[B] 14 cm
[C] 2 cm
[D] 3.5 cm
Answer: 10 cm
(9) The length of the second’s pendulum on the surface of the earth is 1m. The length of the same pendulum on the surface of the moon, where the acceleration due to gravity is (⅙)th of the g on the surface of the earth is
[A] 36 m
[B] 1m
[C] 1/36 m
[D] ⅙ m
Answer: ⅙ m
(10) The mass and diameter of a planet are twice those of earth. The period of oscillation of pendulum on this planet will be (if it is a second’s pendulum on earth)
[A] 1/√2 second
[B] 2 x √2 second
[C] 2 second
[D] ½ second
Answer: 2 x √2 second
(11) The equation of motion of a particle is.

The motion is

[A] Periodic but not oscillatory.
[B] Periodic and oscillatory.
[C] Oscillatory but not periodic.
[D] Neither periodic nor oscillatory.
Answer: Oscillatory but not periodic.
(12) The displacement of a particle varies with time according to the relation.
[A] The motion is oscillatory but not S.H.M.
[B] The motion is S.H.M. with amplitude.
[C] The motion is S.H.M. with amplitude.
[D] The motion is S.H.M. with amplitude.
Answer: The motion is S.H.M. with amplitude.
(13) A particle is acted simultaneously by mutually perpendicular simple hormonic motions and . The trajectory of motion of the particle will be
[A] An ellipse.
[B] A parabola.
[C] A circle.
[D] A straight line.
Answer: A circle.
(14) The displacement of a particle is represented by the equation y=sin3ϖ . The motion is
[A] Non-periodic.
[B] Periodic but not simple harmonic.
[C] Simple harmonic with period 2π/ϖ
[D] Simple harmonic with period π/ϖ
Answer: Periodic but not simple harmonic.
(15) The displacement of a particle is represented by the equation

The motion of the particle is

[A] Simple harmonic with period 2p/ϖ
[B] Simple harmonic with period π/ϖ
[C] Periodic but not simple harmonic.
[D] Non-periodic.
Answer: Simple harmonic with period π/ϖ
(16) A particle is in linear simple harmonic motion between two points A and B, 10 cm apart (Fig. ). Take the direction from A to B as +ve the direction and choose the correct statements.

[A] The sign of velocity, acceleration and force on the particle when it is 3 cm away from A going towards B are positive.
[B] The sign of velocity of the particle at C going towards O is negative.
[C] The sign of velocity, acceleration and force on the particle when it is 4 cm away from B going towards A are negative.
[D] The sign of acceleration and force on the particle when it is at point B is negative.
Answer: A, C, D
(17) A body is performing S.H.M. Then its
[A] Average total energy per cycle is equal to its maximum kinetic energy.
[B] Average kinetic energy per cycle is equal to half of its maximum kinetic energy.
[C] Mean velocity over a complete cycle is equal to 2/π times of its maximum velocity.
[D] Root mean square velocity is 1/√2 times of its maximum velocity
Answer: A, B, D
(18) Which of the following statements is/are true for a simple harmonic oscillator?
[A] Force acting is directly proportional to displacement from the mean position and opposite to it.
[B] Motion is periodic.
[C] Acceleration of the oscillator is constant.
[D] The velocity is periodic.
Answer: A, B, D
(19) Displacement vs. time curve for a particle executing S.H.M. is shown in Fig. Choose the correct statements. Fig.

[A] Phase of the oscillator is same at and.
[B] Phase of the oscillator is same at and.
[C] Phase of the oscillator is same at and.
[D] Phase of the oscillator is same at and.
Answer: D, B
(20) The rotation of earth about its axis is
[A] Periodic motion.
[B] Simple harmonic motion.
[C] Periodic but not simple harmonic motion.
[D] Non-periodic motion.
Answer: A, C

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