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http://loncapa2.physics.sc.edu/res/sc/gblanpied/courses/usclib/hrw8/hrwpictures/10-31.jpg Two cars A and B slide on an icy road as they attempt to stop at a traffic light. The mass of A is 1100 kg, and the mass of B is 1450 kg. The coefficient of kinetic friction between the locked wheels of either car and the road is 0.18. Car A succeeds in coming to rest at the light, but car B cannot stop and rear-ends car A. After the collision, A comes to rest 8.2 m ahead of the impact point and B 6.1 m ahead; see the figure. Both drivers had their brakes locked throughout the incident. From the distance each car moved after the collision, find the speed of each car immediately after impact. Speed of A? Speed of B? Use conservation of linear momentum to find the speed at which car B struck car A. On what grounds can the use of linear momentum conservation be criticized here: (none, gravity, kinetic, destruction, friction) A) none B) destruction C) friction D) kinetic E) gravity

Explanation / Answer

Deceleration of each car will be equal to .18*g = 1.764 m/s^2 For car A , v = sqrt(2*1.764*8.2) = 5.38 m/s ....similarly for car B, v = sqrt(2*1.764*6.1) = 4.64 m/s ....Let initial velocity of car B = v then, applying conservation of linear momentum 1450*v = 1100*5.38 + 1450*4.64 ..........on solving, v = 8.72 m/s ...............Use of linear momentum conservation can be criticized on the grounds of B) destruction due to collision between the two cars

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