a 920 kg sports car collides into the rear end of a 2300 kg SUV stopped at...

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Katryn

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...a red light. the bumpers lock, the? a 920 kg sports car collides into the rear end of a 2300 kg SUV stopped at a red light. the bumpers lock, the brakes are locked, and the two cars skid forward 2.1 m before stopping. the police officier knowing that the coefficient of kinetic friction is 0.42 calculates the speed of the sports car at impact
 
mg = (920 x 9.8) + (2300 x 9.8) = 31556 N

friction force = 31556 x 0.42 = 13253.52

work done = force x distance = (13253.52 x 2.1) = 27832.392 J

27832.392 = 1/2mv^2

27832.392/(0.5 x 920) = v^2 = 60.5052, sq-root = v = 7.78 m/s
 
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