You have been called to testify as an expert witness in a trial involving a head

Question

You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 660.0 kg and was traveling eastward. Car B weighs 490.0 kg and was traveling westward at 64.0 km/h. The cars locked bumpers and slid eastward with their wheels locked for 6.00 m before stopping. You have measured the coefficient of kinetic friction between the tires and the pavement to be 0.750.

1)How fast (in kilometer per hour) was car A traveling just before the collision? (Express your answer to three significant figures.)

Explanation / Answer

1] Velocity of combines mass, v= sqrt(2as) where a =ug

= sqrt(2*0.75*9.8*6) = 9.39 m/s = 9.39*18/5 km/h

m1v1 + m2v2 = (m1+m2)v

660v1 - 490*64 = (660+490)*9.39*18/5 = 38875

v1 = [38875 + 490*64]/660

= 106 km/h answer

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