[问答题]
A child on a sled comes flying over the crest of a small m*qs+3aa8, ijtmhit g 2tp i(,hill, as shown in Fig.9 2(ei /y2, lmodl9sxh*l ngju 5–31. His sled does not leave the ground (he does ml9 leld (xgh*n29/2s,u jiyonot achieve “air”), but he feels the normal force between his chest and the sled decrease as he goes over the hill. Explain this decrease using Newton’s second law.
