Question 1: The three points O, A, B and located on a half line derived from O. O located at a point source isotropic sound broadcasting into space, the environment does not absorb sound. A sound intensity level is at 60dB and 20dB at B is. CD sound level at the midpoint M of segment AB? (A: 26dB)

Question 2: CLLX harmonic oscillation with T and BDO cky 5cm. Said in a cky, about small things tgian to the magnitude of the pendulum is accelerated EXCEED 100cm/s2 is T / 3. Ddong the frequency of animal? (Answer: 1Hz)

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