A Hot Air Balloon of Radius 10m Is Floating at a Constant

question 5

Multiple Choice

A hot air balloon of radius 10m is floating at a constant altitude over Parliament House in Canberra. It is initially at rest. Suddenly, an easterly breeze of speed 10 cm s-1 starts blowing. Assuming that Stokes' law applies, how much force does the wind apply to the balloon? The viscosity of air is 1.8x10-5 Pa s.

• A) 3.4x10-5 N
• B) 3.4x10-4 N
• C) 3.4x10-3 N
• D) 3.4x10-2 N
• E) 3.4x10-1 N
• ANS