# Chapter 14 - Think and Explain: 85

The comparison is done in Figure 14.21 on page 274. The spacing of streamlines around a non-spinning ball doesn't vary much. The streamlines around a spinning ball are closer on the side where the surface is spinning toward the forward direction (because the speed of the air with respect to the surface is increased). The pressure difference (explained by Bernoulli's principle) on opposite sides of the ball causes a force, making the ball veer.

#### Work Step by Step

This is discussed on page 274.

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