解:(1)mgx=, 32x2,xs3 mg =0.49m k (2) o = mo ,x0=m2g/=0.245m mg xo=mu2+=J 002 o 2 2 0o=k(m+/R2)2mg =1.3m·s 作业:5.115.125.135.15516, 2 1 (1) 2 mgx = kx k mg x 2 = = 0.49m (2) , kx0 = mg x0 = mg / k = 0.245m mg x mv J kx 2 0 2 0 2 0 0 2 1 2 1 2 1 = +  + v k(m J /R ) mg 2 2 1 0 = + − -1 =1.3m  s 解： 作业： 5.11 5.12 5.13 5.15 5.16