[填空题]
When you are runningmi,ylqees8 k:f-3ds-1 mc rj ) and want to stou -o:dtaqx p*2b:/jyby:(tajp quickly, you must decelerate quickly. (a) What is the origin of the force that causes you to stop? (b) Estimate (using your own experiencj: a-t( 2a/ db:bp:q tyxoyj*ue) the maximum rate of deceleration of a person running at top speed to come to rest. m/s$^2$
