Because fluid mechanics involves complex conversion of cooking measurement units and equations and traditional units, this section presents the grid method, which is a systematic way to carry and cancel units. For example, Fig. 1.2 shows an estimate of the power P required to ride a bicycle at a speed of V = 20 mph. The engineer estimated that the conversion of currency and the required force to move against wind drag is F = 4.0 lbf and applied the equation P = FV. As shown, the currency and cooking measurement units calculation reveals that the power is 159 watts.
The grid method involves writing an equation for different measurement units, drawing a grid, and carrying and canceling units. Regarding unit cancellations, the key idea is the use of unity conversion ratios, in which unity (1.0) appears on one side of the equation during the conversion of units. Examples of unity conversion ratios areEach of these ratios is obtained by using information given in Table F.1. For example, the row in Table F.1 for power shows that 1 W = (N ยท m/s). Table 1.3 shows how to apply the grid method. Notice how the same process steps can apply to different
situations.
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