|
|
S E C T I O N 4 . 6 • Relative Velocity and Relative Acceleration 97 then straight downward along the same vertical line, as shown in Figure 4.22a. An ob- Another example of this concept is the motion of a package dropped from an air- plane flying with a constant velocity—a situation we studied in Example 4.6. An ob- In a more general situation, consider a particle located at point ! in Figure 4.23. Imagine that the motion of this particle is being described by two observers, one in ref- v 0 . (Rel- ative to an observer in S$, S moves to the left with a velocity # v 0 .) Where an observer stands in a reference frame is irrelevant in this discussion, but for purposes of this dis- (a) (b) Path seen by observer B A A Path seen by observer A B Figure 4.22 (a) Observer A on a moving skateboard throws a ball upward and sees it rise and fall in a straight-line path. (b) Stationary observer B sees a parabolic path for the same ball. S r r ′ v 0 t S ′ O ′ O v 0 ! Figure 4.23 A particle located at ! is de- scribed by two observers, one in the fixed frame of reference S, and the other in the frame S$, which moves to the right with a constant velocity v 0 . The vector r is the par- ticle’s position vector relative to S, and r$ is its position vector relative to S$. |