An airplane has an effective wing surface area of 17.0 m2 that is generating the lift force. In level flight the air speed over the top of the wings is 55.0 m/s, while the air speed beneath the wings is 40.0 m/s. What is the weight of the plane?

Respuesta :

To solve this problem it is necessary to apply the equations given from Bernoulli's principle, which describes the behavior of a liquid moving along a streamline. Mathematically this expression can be given as,

[tex]P_1 + \frac{1}{2}\rho*v_1^2 + P_2 + \frac{1}{2}*\rho*v_2^2=0[/tex]

Where,

[tex]P_i =[/tex] Pressure at each state

[tex]\rho[/tex]= Density

[tex]v_i =[/tex] Velocity

Re-organizing the expression we can get that

[tex]P_1 - P_2 = \frac{1}{2}\rho (v_2^2 - v_1^2)[/tex]

Our values are given as

[tex]v_1 = 40m/s[/tex]

[tex]v_2 = 55m/s[/tex]

[tex]\rho_{water} = 1.2kg/m^3 \rightarrow[/tex] Normal Conditions

Replacing we have,

[tex]P_1 -P_2 = \frac{1}{2}*1.2*(55^2-40^2)[/tex]

[tex]P_1 - P_2 = 855Pa[/tex]

If we consider that there is a balance between the two states, the Force provided by gravity is equivalent to the Support Force, therefore

[tex]F_l = F_g[/tex]

Here the lift force is the product between the pressure difference previously found by the effective area of the aircraft, while the Force of gravity represents the weight. There,

[tex]F_g = W[/tex]

[tex]F_l = (P_2-P_1)A[/tex]

Equating,

[tex](P_1 - P_2)*A = W[/tex]

[tex]W = 855*17[/tex]

[tex]W = 14535 N[/tex]

Therefore the weight of the plane is 14535N