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c. 1024/9.

d. 64/9.

6.
Two pendula of lengths 121 cm and 100 cm start vibrating. At some instant the
two are in the mean position in the same phase. After how many vibrations of the
shorter pendulum, the two will be in the same phase in the mean position

a. 10 vibrations.

b. 11 vibrations.

c. 21 vibrations.

d. 20 vibrations.

7. Due to some force F1 a body oscillates with period 4/5 s and due to other force F 2 it
oscillates with period 3/5 s. If both the forces acts simultaneously new period will be
a. 0.72 s

b. 0.64 s

c. 0.68 s

d. 0.36 s

8. The time period of a simple pendulum measured inside a stationary lift is T. If the lift
starts moving upward with an acceleration g/3, its time period will be:

a.

b.

c.

d.
9.
A mass M attached to a spring oscillates with a period of 2 seconds. If the mass is
increased by 2 kg, the period increases by one second. Then the initial mass M is

a. 3.6 kg.
b. 2 kg.

c. 1.6 kg.

d. 0.4 kg.

10. The amplitude of a damped oscillator becomes 1/27th of its initial value after 6 min. What
was the amplitude after 2 minutes?

a. one-ninth

b. one-sixth

c. one-third