# Homework Help: Car Question

1. Oct 15, 2006

### kara

Car Question !!!

Two Jeeps P and B race along straight lines, across flat terrain, and past stationary border guard A. Relative to the guard, B travels at a constant speed of 20.0 m/s at the angle theta=30.0*. Relative to the guard, P has accelerated from rest at a constant rate of 0.400 m/s^2 at the angle theta2=60.0*. At a certain time during the acceleration, P has a speed of 40.0 m/s. At that time I need to find magnitude and direction of the velocity of P relative to B, and the magnitude and direction of the acceleration of P relative to B?

Besides a basic diagram I honestly have no idea where to start. Can anyone point me in some direction to get the ball rolling???

2. Oct 15, 2006

### OlderDan

The statement of the problem is a little nonsensical. Angles can only be measured relative to directions, not points. That can be fixed by interpreting the angles as relative to some line through the guard, perhpas the direction he is looking. Since the problem only asks you to deal with velocity and acceleration, the positions of P and B do not really matter. What matters is the components of velocity and acceleration and their differences. If you use the reference line as one axis, and another perpendicular axis, fixed relative to the ground (the guard) you can resolve the velocity and acceleration components along those axes. The "relative" quantities are the differences between the absolute quantities in the coordinate system you have made.