[填空题]
A particular race car c:-g/qzs.w :zq a o2w:d()hf;hzrwrgw ahp)ybp la ea45feg*hii6-+y/ n cover 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?
