[填空题]
A 920-kg sports car collides into the rear end of a 2300-kg SUV sp.n6 o.o6faj*th *u8cg 0n ycjtoppbq: dcyal31fw.z-4wk4 m:y au ed at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 2.8 m before stopl f43u:w kqmw. :1cb4-aa dyyzping. The police officer, knowing that the coefficient of kinetic friction between tires and road is 0.80, calculates the speed of the sports car at impact. What was that speed?(Let A represent the sports car, and B represent the SUV) $\approx$ m/s
