4. A new design of telecommunications tower is modelled as a 5m diameter perfectly smooth

sphere on top of a vertical perfectly smooth cylinder, 30m high and 2m diameter. It has to

withstand an aerodynamic force imposed by a 100 km/h wind. For air take the density to

be 1.20 kg/m³ and the kinematic viscosity to be 1.5 x 10-5 m²/s.

a) Determine the aerodynamic drag force acting on the sphere.

b) Determine the aerodynamic drag force acting on the cylinder.

c) Estimate the bending moment at the base of the tower.

[7 marks]

[7 marks]

[5 marks]

d) Discuss why these results should only be regarded as an estimate of the influence of

drag on the real tower.

[6 marks]