Calculate Drag Force for Tennis Ball at 251 km/h

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SUMMARY

The discussion focuses on calculating the drag force acting on a tennis ball served at a speed of 251 km/h. The relevant formula for drag force is Fd = π * d² * CD * pf * u² / 4. Key parameters include the ball's diameter of 6.5 cm, air density of 1.3 kg/m³, and air viscosity of 1.8 x 10⁻⁵ kg/m·s. A significant error was identified in the conversion of speed from km/h to m/s, which affects the calculation of the Reynolds number.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with drag force calculations
  • Knowledge of Reynolds number and its significance
  • Proficiency in unit conversions, particularly speed
NEXT STEPS
  • Learn about the calculation of Reynolds number in fluid dynamics
  • Study the relationship between drag coefficient and Reynolds number
  • Explore the effects of air viscosity on drag force
  • Practice unit conversions, specifically from km/h to m/s
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Physics students, engineers, and anyone interested in the dynamics of sports equipment and aerodynamics.

steve978
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Homework Statement



A tennis player hit a serve of 251 km.h-1 in a match. Calculate the Drag Force acting on the tennis ball. Diameter of ball is 6.5cm, density of air is 1.3 kg.m-3 and air viscosity is 1.8x10-5 kg.m-1.s-1.

Homework Equations



Drag Force is: Fd= \pi.d2.CD.pf.u2.1/4

The Attempt at a Solution



My attempt is to find Reynolds number: Rep = (pfutdp)/u = (1.3)(903,600,000)(0.065)/0.000018
and then use a graph of drag coefficient against Rep to find Cd. However my number for Re is 4.24E+13 which is far too large to be correct. Is there something i am doing wrong?
 
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Hello steve978.

Check your conversion of km/h to m/s.
 

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