[填空题]
When you are running andsqeet qo-z10+uf1yj )kj /2awl0 n4a*qi .upm want to stop quickly, you must decelerate quickly. (a) What is th)jawuu mf0*1p ql./ay2jikn4 e origin of the force 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$^2$
