Homework Help: Relative motion of two cars (velocity and acceleration)

1. Apr 16, 2015

Chris T.

1. The problem statement, all variables and given/known data
Cars A and B are traveling on adjacent roads. Car A travels at a speed of 70 mi/h in the positive y direction, and its acceleration is zero. Car B travels along a circular path of radius 0.7 mi, and has a velocity of 50 mi/h at an angle of 30 degrees right of vertical. Car B has an acceleration of 1100 mi/h^2. Find the relative velocity and acceleration of car B with respect to Car A.

2. Relevant equations
v(B wrt A) = v(B) - v(A) (vector velocities)
a(B wrt A) = a(B) - a(B) (vector accelerations)
3. The attempt at a solution
I started by writing the velocity of both A and B in their own inertial frames, in vector form (cartesian coordinates). Car A has velocity 0i+70j, and Car B has velocity 50sin(30)i+50cos(30)j. By subtracting the velocity of A from the velocity of B, I got the correct magnitude and direction of the relative velocity that is being asked for. I am now stuck looking at how to approach the relative acceleration portion of the question. Any help is greatly appreciated?

2. Apr 16, 2015

dcrisci

Its kind of hard to help with no solution of yours to see where you're going wrong. However remember that car b is going in a circular motion and the acceleration will always be directed towards the centre of the circle (perpendicular to its direction of motion along the curve). Perhaps you didn't do this and used wrong directions for the acceleration vector of car b.