3. What are the units for Coeffecient of Lift?
[kgm^-3]
No units
[Ns]
[N^2]
[N]
[ms^-1]
[kg]
4. What are the units for the ratio Lift to Drag?
[Ns]
[kgm^-3]
No units
[ms^-1]
[kg]
[N^2]
[N]
To find the units for the Coefficient of Lift and the ratio Lift to Drag, we need to understand their definitions and how they are calculated.
The Coefficient of Lift (CL) is a dimensionless quantity that represents the lift generated by an object, such as an airplane wing, compared to the dynamic pressure of the airflow around it. It is calculated by dividing the lift force by the product of the dynamic pressure and the reference area. The formula for calculating CL is:
CL = Lift / (0.5 * ρ * V^2 * A)
where:
- Lift is the force perpendicular to the flow direction (N)
- ρ (rho) is the density of the fluid (kg/m³)
- V is the velocity of the fluid (m/s)
- A is the reference area (m²)
From the formula, we can see that the units of CL are N / (0.5 * kg/m³ * m/s * m²), which simplifies to N / (kg/m²) or Nm^-2.
Therefore, the units for the Coefficient of Lift are [Nm^-2].
Moving on to the ratio Lift to Drag (L/D), it represents the efficiency of an object in generating lift compared to the drag it produces. It is also a dimensionless quantity and is calculated by dividing the Lift by the Drag force. The formula for calculating L/D is:
L/D = Lift / Drag
where both Lift and Drag have the same units.
Since both Lift and Drag forces have units of Newtons (N), the units for the ratio Lift to Drag are [N/N], which simplifies to no units.
So, the correct units for the Coefficient of Lift are [Nm^-2] and the correct units for the ratio Lift to Drag are no units, or simply, dimensionless.