A well-hit golf ball travels about 300 yards. A fast bowler or fastball pitcher throws a cricket ball or baseball at more than 90mph (miles per hour). A table-tennis player can hit a forehand return at about 30mph. The masses and diameters of each of these four types of balls are m_g ∼ 46 g, d_g ∼ 43 mm; m_c ∼ 160 g, d_c ∼ 70 mm; m_b ∼ 140 g, d_b ∼75 mm; and m_tt ∼ 2.5 g, d_tt ∼ 38 mm.

(a) For golf, cricket (or baseball), and table tennis, estimate the Reynolds number of the flow and infer the drag coefficient C_D. (The variation of C_D with Re_d can be assumed to be similar to that in flow past a cylinder; Fig. 15.2.)

Fig. 15.2.

(b) Hence estimate the importance of aerodynamic drag in determining the range of a ball in each of these three cases.

Transcribed Image Text:

CD 100 10 1 0.1 0.1 CD-6/Red 1 10 I 100 103 Red 104 boundary layer becomes turbulent 105 T 106