Step-by-step solution would be much appreciated! Need this urgently! You have be

Question

Step-by-step solution would be much appreciated! Need this urgently!

You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 1515 lb and was traveling eastward. Car B weighs 1125 lb and was traveling westward at 46.0 mph. The cars locked bumpers and slid eastward with their wheels locked for 17.5 ft before stopping. You have measured the coefficient of kinetic friction between the tires and the pavement to be 0.750. How fast (in miles per hour) was car A traveling just before the collision? (This problem uses English units because they would be used in a U.S. legal proceeding.)

Explanation / Answer

1 lb = 0.45 kg

1515 lb = 687.19 kg

1125 lb = 510.29 kg

45 m/s = 20.11 m/s

17.5ft= 5.334 m

converstaoin of linear momentum

687.19*u - 510.29*20.11 = (687.19+510.29)*V

but given according to friction they stop

so

0.5* (687.19+510.29)*V*V = 0.75* (687.19+510.29)*9.8*5.334

V = 8.854 m/s

from this we get u =30.36 m/s = 67.89 milesperhour

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