Question

Wind is blowing to a circular sign board with the velocity of 100km/hr . Calculate the drag force on the circular sign board of the diameter is 2.5metre . Assume that the air is at 27°C and 101kpa, and drag coefficient is 1.3​

Answer 1

Given Info : Wind is blowing to a circular sign board with the velocity of 100 km/h. diameter of sign board is 2.5 m. assuming that the air is at 27°C and 101 Kpa and drag coefficient is 1.3.

To find : the drag force on the circular sign board is...

solution : using formula, F = μ × ρ × v² × A/2

where μ = coefficient = 1.3

ρ = density of the air = 1.25 kg/m³

v = speed of wind = 100 km/h = 100 × 5/18

= 27.78 m/s

A = πr² = 3.14 × (2.5/2)² = 3.14 × 1.5625

= 4.90625 m² ≈ 4.9 m²

now, F = 1.3 × 1.25 × (27.78)² × (4.9)/2

= 1.3 × 1.25 × 771.7284 × 2.45

= 3,072.44369 N ≈ 3072.44 N

Therefore the drag force on the circular sign board is 3072.44 N.