Teaching Physics with the Physics Suite Edward F. Redish

Blast off!

A two stage rocket starts firing its engines at a time t = 0. From that instant, it begins to move upwards with a constant acceleration. This continues until a time t1. The rocket drops the first stage and continues upward briefly until a time t2 at which point the second stage begins to fire and the rocket again accelerates upward, this time with a larger (but again constant) acceleration. Sometime during this second period of acceleration, our recording apparatus stops.

1. On copies of the graphs below, sketch qualitatively accurate (i.e., we don't care about the values but we do about the shape) graphs of each of the height of the rocket, y, its velocity, v, its acceleration, a, the force of the engine on the rocket, Fe->r, and the net force on the rocket, Fnet. Take the positive direction as upward.

2. How can you check for coherence between your acceleration and your net force graph? Briefly explain how to do it and explain why that strategy works.

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