Express your answer in terms of the momenta of the two cars, and?

Question

Two cars of masses m1 and m2 collide at an intersection. Before the collision, car 1 was traveling eastward at a speed of v1 , and car 2 was traveling northward at a speed of v2. After the collision, the two cars stick together and travel off in the direction shown.

1,First, find the magnitude of v(vector), that is, the speed v of the two-car unit after the collision
Express v in terms of m1,m2 , and the cars' initial speeds v1 and v2.

2,Find the tangent of the angle (theta).
Express your answer in terms of the momenta of the two cars,p1 and p2


for that problem i put p1/p2 and its wrong they told me look at the figure given if p2=0 what should tan(theta) be? and im so confused now any boddy can help me pliz

Answer 1

Despite this ain't Yahoo! Answers My Homework, here are some answers to your request
http://answers.yahoo.com/question/index;_ylt=Ahsc99BD0uHiFynXd47GzMLsy6IX?qid=20061016090643AAklkTV

Answer 2

The collided cars go off at some angle ø (let's say measured from the vertical) Momentum is conserved in each direction. The east-west momentum (after collision) is then (m1+m2)*v*sinø and the north-south momentum is (m1+M2)*v*cosø. The east-west momentum of the whole system before collision is just that of the eastward car, p1 = m1*v1, and similarly for the north-south momentum p2 = m2*v2; summing before and after momenta for each direction:

m1*v1 = (m1*m2)*v*sinø

m2*v2 = (m1+m2)*v*cosø

You have two equations in two unknowns, v and ø; you can solve.