Passage IV

Two types of friction affecting bicycle riders are:

· air resistance

· rolling resistance between the tires and the ground

Table 1 gives the air resistance, RA, affecting a rider moving at speed V when the cross-sectional area of the rider plus bicycle equaled X. Table 1 also gives the power, PA, in watts (W), the rider had to generate to compensate for RA to maintain V. Figure 1 gives the power, PA + R, in horsepower (hp), a rider had to generate to compensate for RA plus rolling resistance to maintain V = 5.6 m/sec or 11. 2 m/sec for a wheel diameter of 16 inches or 27 inches and various tire pressures. Figure 2 is a graph of power in W versus power in hp.

Figure 1 adapted from Frank Roland Whitt and David Gordon Wilson, "Bicycling Science." @1974 by The Massachusetts institute of Technology.

21. A student suggested that for the rider to maintain a speed of 11. 2 m/sec on a bicycle with 27 inch wheels, PA+R would be less if the tire pressure were 80 1b/in than if the tire pressure were 140 1b/in2. Does Figure 1 support the student's suggestion?

Answer and Explanation

Your Answer is

Correct Answer is D

Explanation

Looking at the curve of V=11.2, 27 inches wheel in figure 1, as the abscissa tire pressure increases, the ordinate decreases, so the statement in the question stem is wrong