Important Questions for competitive Exams : Physics 1

1. The simple harmonic motion of a particle is given by y = 3 sin wt + 4 cos wt
What is the amplitude?
   (1) 1
   (2) 7
   (3) 5 ✔
   (4) 12
2. If the magnitude of displacement is numerically equal to that of acceleration, then the time period is :
   (1) 1 second
   (2) π second
   (3) 2π second ✔
   (4) 4π second
3. If the mass of an oscillator is numerically equal to its force constant, then the frequency is :
   (1) π
   (2) 2π
   (3) 1/π
   (4) 1/2π ✔
4. Time period of oscillation of a spring is 12 s on the Earth. What shall be the time period if it is taken to Moon?
   (1) 12 s ✔
   (2) 12/6 s
   (3) 12×6 s
   (4) 16×√12 s
5. What shall be the time period of a simple pendulum in a freely falling lift?  Given : T = time period of the pendulum in the lift at rest.
   (1) T
   (2) 2T
   (3) T/g
   (4) infinite  ✔
6. What is the minimum time taken by a particle in SHM of time period T from the point of maximum displacement to that at which the displacement is half the amplitude?
   (1) T/4
   (2) T/8
   (3) T/12
   (4) T/6  ✔
7. The equation of SHM of a particle is a + 4π²x = 0, where a is instantaneous linear acceleration at displacement x. The frequency of motion is :
   (1) 1 ✔
   (2) 4π
   (3) 1/4
   (4) 4
8. A particle performs simple harmonic motion along a line 4 cm long. The velocity of the particle when it passes through the mean position is π m/s. The period of SHM is :
   (1) 0.01 s
   (2) 0.04 s ✔
   (3) 0.8 s
   (4) 0.6 s
9. The time period of a mass suspended from a spring is 5 s. The spring is cut into four equal parts and the same mass is now suspended from one of its parts. The period is now
   (1) 5 s
   (2) 2.5 s  ✔
   (3) 1.25 s
   (4) 5/16 s
10. The time period of a second's pendulum is 2 s. The spherical bob which is empty from inside has a mass of 50 g. This is now replaced by another solid bob of the same radius but having a different mass of 100 g. The new period will be :
   (1) 4 s
   (2) 1 s
   (3) 2 s ✔
   (4) 8 s
11. For a simple pendulum, the graph between l and T is :
   (1) hyperbola
   (2) curved line
   (3) straight line
   (4) parabola  ✔
12. The velocity and acceleration of a particle executing SHM have a steady phase relationship. The acceleration leads velocity in phase by :
   (1) + π
   (2) + π/2 ✔
   (3) – π/2
   (4) – π
13. A clock P is based on oscillation of a spring and another clock Q is based on pendulum motion. Both the clocks run at the same rate on Earth. Both the clocks are then taken to a planet having same density as Earth but twice the radius. Then
   (1) P will run faster than Q.
   (2) Q will run faster than P. ✔
   (3) both will run at the same rates as on Earth.
   (4) both will run at equal rates but faster than on Earth.
14. Two simple harmonic motions have amplitudes 4 cm and 7 cm. The difference in phase is π/2. The resultant amplitude is :
   (1) 4 cm
   (2) 7 cm
   (3) √65 cm ✔
   (4) 3 cm
15. One spring has force constant 200 N/m, another has force constant 500 N/m. If they are joined in series, the force constant will be nearest to
   (1) 700 N/m
   (2) 300 N/m
   (3) 143 N/m  ✔
   (4) 100 N/m
16. The tension in the string of a simple pendulum is
   (1) constant
   (2) maximum in the extreme position
   (3) zero in the mean position
   (4) none of  these  ✔