[填空题]
When you are running and iz(i7f ;x/gszj .xnl3 want tubn n t*2k5p/.61a8y)k;joimkghpf to stop quickly, you must decelerate quickly. (a) What is the origin of the foom*/gn1iph fpk) tauk56 b8j.y2t k n;rce that causes you to stop? (b) Estimate (using your own experience) the maximum rate of deceleration of a person running at top speed to come to rest. m/s$^2$
