已知：M=50kgw=0.41=4mv=4m/s 求：(1)a=0N=? (2)a=0.2m/s2W=? 解：（1)2f-Mg=Ma a=0 2f=M f=uN Mg N-2μ =613N Mg (2)a=0.2m/s2 M(g+a)50(9.8+0.2) N= 625N 2u 2×0.4 结已知：M= 50kg m =0.4 l = 4m v= 4m/s 求：(1 ) a = 0 N = ? (2 )a = 0.2m/s2 N = ? 解：(1 ) 2f Mg =M a a = 0 2f =Mg f = mN = Mg 2m N = 613N (2 ) a = 0.2m/s2 = a = M g 2m N = ( + ) 50 9.8 0.2 2× 0.4 ( + ) 625N M g f N f N 结束 目录