[填空题]
A particular race cak8q+ckr ckdg7b1 n4dp 0a8;bl au urt:14,hxcr can covea ki+jlbh50 4v7gsw i8r a quarter-mile track (402 $\mathrm{~m}$) in 6.40 s starting from a standstill. Assuming the acceleration is constant, how many " g 's" does the driver experience? If the combined mass of the driver and race car is 485 kg , what horizontal force must the road exert on the tires?
