Physics for Scientists and Engineers 3E by R. Knight, C1E&P9

Figure Ex 1.9 shows the first three points of a motion diagram. Is the object’s average speed between points 1 and 2 greater than, less than, or equal to its average speed between points 0 and 1? Explain how you can tell.

Use Tactics Box 1.3 to find the average acceleration vector at point 1. Draw the completed motion diagram, showing the velocity vectors and acceleration vector.

Figure Ex1.9

Solution:

Solve

Part a

Let $\displaystyle \vec{v_0}$ be the velocity vector between points 0 and 1 and $\displaystyle \vec{v_1}$ be the velocity vector between points 1 and 2. Speed v₁ is greater than v₀ because more distance is covered in the same interval of time.

Part b

To find the acceleration, use the method of Tactics Box 1.3:

Figure 1.9 Answer Physics for Scientists and Engineers by Randall Knight

Assess

The acceleration vector points in the same direction as the velocity vectors, which makes sense because the speed is increasing.

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