[填空题]
An earthquake-produced surface wave canni+ b;g3lodv5 bo ;3pevhuljw7g ;zuxp.ls v x+ v5+p72e approximated by a sinusoidal transverse wave. Assuming a frequency of 0.50 Hz (typix3 uzewxh +2u 7sg v+ppplljo v;5;v7.cal of earthquakes, which actually include a mixture of frequencies), what amplitude is needed so that objects begin to leave contact with the ground? [Hint: Set the acceleration a>g] m
