Answer:
Fthrust = 110.99 kN
Explanation:
Model:
Ignore the drag on the wings and focus on the cylindrical fuselage.
Visualize:
The net force is zero as the jet cruises at 230 m/s, so the thrust must be equal in magnitude to the drag. The gravitational and lift forces are equal in magnitude and opposite in direction.
Given
D = 3.80 m ⇒ R = D / 2 = 3.80 m/ 2 = 1.90 m
C = 0.37
ρ = 1.0 kg/m³
v = 230 m/s
m = 85,000 kg
Fthrust = ?
We show the Free Body Diagram in the pic.
Then, we apply
∑Fx = 0 (→+)
Fthrust = Fdrag = (1/2)*C*ρ*A*v²
A = π*R² = π*(1.90 m)² = 11.34 m²
⇒ Fthrust = (1/2)*(0.37)*(1.0 kg/m³)*(11.34 m²)*(230 m/s)²
⇒ Fthrust = 110990.159 N = 110.99 kN
