Question

As per Kutta--Joukowski Theorem, lift per unit span is directly proportional to

• A. Circulation strength
• B. Temperature
• C. Acceleration
• D. Chord length

Hint:

Kutta--Joukowski Theorem: \[ \boxed{ L'=\rho V_{\infty}\Gamma } \] Thus, \[ \boxed{ \text{Higher circulation} \Longrightarrow \text{Higher lift.} } \]

Answer 1

The Correct Option is A

Step 1: Recall the Kutta--Joukowski theorem. The lift per unit span acting on an airfoil is \[ \boxed{ L'=\rho V_{\infty}\Gamma, } \] where
• \(L'\) = lift per unit span,
• \(\rho\) = fluid density,
• \(V_{\infty}\) = free-stream velocity,
• \(\Gamma\) = circulation strength.

Step 2: Identify the directly proportional quantity. From the equation, \[ L' \propto \Gamma. \] Hence, \[ \boxed{\text{Lift per unit span is directly proportional to circulation strength}.} \] Therefore, \[ \boxed{\text{Circulation strength}} \] is the correct answer. Thus, \[ \boxed{(A)} \] is the correct answer.