(1)E=1/2kA² =1/2*2.0*0.2²J =0.04JE/2=1/2kx²0.04/2=1/2*2.0x²x=0.14m(2)Acosθ=x0.2cosθ=0.14θ=45°T=2π(m/k)^1/2 =2π(0.5/2.0)^1/2 =π所以所求时间为：t=T/8=π/8请自己再计算验算一遍
