You have been hired as an expert witness in a court case involving an automobile

Question

You have been hired as an expert witness in a court case involving an automobile accident.  Mass of Car A is 1900kg, which crashes into stationary Car B, Mass 1100kg.  Car A began breaking 15m before hitting Car B.  After colliding, Car A slides 18m and Car B slides 30m (Car A slides 18m, while Car B slid 30m, Im assuming they slid the first 18m together??)  The coefficient of kinetic friction between the locked wheels and the road is 0.60.  Show that the driver of Car A was exceeding the 55mp/h (90km/h) speed limit before hitting the breaks

Explanation / Answer

      = .6    mass -A = 1900    mass - B = 1100    distance A = 15 m    distance B slides = 18 m    distnace A slides = 30 m       suppose vel = 90 km/ hr = 25m/s    deceleration = N/mass =-5.88 m/s^2    vel @ end of 15 m =square root ( u^2- 2aS) = 21.18 m/s
   After Collision-----    common vel = 13.414m/s          now thru energyconsevation/.......    for block A......    .5 (Mass of A) x (vel^2)= fr x S(= 18 mt) +.5 x Mass of b x ( final Vel ^2)    the final vel = 0 ........thus thebody comes to rest...    putting the same for B.........withS= 30 mt.........we get the final vel = 0/.....


   hope this gets u thru theconcept...!!!! (;
        

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