Two automobiles traveling at right angles to each other collide and stick together.Car A has a mass of 1200 kg and had a speed of 25 m/s before the collision.Car B has a mass of 1600 kg.The skid marks show that,immediately after the collision,the wreckage was moving in a direction making an angle of 40° with the original direction of car A.What was the speed of car B before the collision,assuming that any other unbalanced forces are negligible?
A) 16 m/s
B) 18 m/s
C) 11 m/s
D) 21 m/s
E) 14 m/s

Question

Quizplus · Accepted Answer

Explanation:Momentum is conserved in both the x and y directions.In the x direction:(1200 kg)(25 m/s) + (1600 kg)(v_B)cos40° = (2800 kg)(v_f)cos40°In the y direction:(1600 kg)(v_B)sin40° = (2800 kg)(v_f)sin40°Dividing the first equation by the second equation, we get:(1200 kg)(25 m/s) + (1600 kg)(v_B)cos40° = (2800 kg)(v_f)cos40°(1200 kg)(25 m/s) + (1600 kg)(v_B)cos40° = (2800 kg)(v_f)cos40°v_B = 16 m/s

Two Automobiles Traveling at Right Angles to Each Other Collide