# Calculate the pressure coefficient at a point on the airfoil.

Calculate the pressure coefficient at a point on the airfoil where the pressure is \( 8.9 \times 10^4\,N/m^2\). Airfoil is in freestream velocity of \(40\,m/s \) and is at standard sea – level conditions.

Pressure coefficient is given as

\[{C_p} = \frac{{p\, – \,{p_\infty }}}{{{q_\infty }}}\]

Dynamic pressure,

\[{q_\infty } = \frac{1}{2}{\rho _\infty }V_\infty ^2 = \frac{1}{2} \times 1.225 \times {\left( {40} \right)^2} = 980\]

Therefore, \(C_p\) is

\[{C_p} = \frac{{0.89 \times {{10}^5} \,-\, 1.01 \times {{10}^5}}}{{980}} =\, – 12.24\]