[填空题]
A 220-kg wooden raft floats on a lake. cco5f 9zuuxhi32l()xo*x z2 n When a 75-kg man standswq5-u 8h6*esa.)k0 ttxru(q xuc s xa6 on the raft, it sinks 4.0 cm deeper into the water. When hkts0r 8.6) c-*qextw uu(a6x5a xushqe steps off, the raft vibrates for a while.
(a) What is the frequency of vibration?(round to one decimal place) $\approx$ Hz
(b) What is the total energy of vibration (ignoring damping)?(Round to the nearest intege) $\approx$ J