quest

Sign in to start training

quest keeps your progress, streaks, and scores tied to your account — so you can pick up on any device.

Synced everywhere. Progress follows you across laptop and phone.

Streaks & stats. See your daily run and every score over time.

Your profile. A name and avatar for the work you do here.

We only use Google to sign you in and sync progress. No posting, no contacts — ever.

Aerodynamics Intermediate

02 The Lift Equation

Everything so far compresses into one line: L = 12 ρ V² S C_L Density, speed squared, wing area, and a coefficient hiding the shape and the angle. This lesson is pure calculation. Work in SI units, state the unit with every answer, and round only at the end; answers are checked against a tolerance, not a keyword list.

Step 3 / 4

In steady level flight, lift equals weight. That same aircraft weighs W = 14700 N (about 1500 kg). With S = 16 m² , flaps giving C_L = 1.2 , and sea-level air, find the slowest speed that still holds altitude: V = √2Wρ S C_L . Answer in m/s.

Hints

Rearranging the lift equation for V is the whole trick: set L = W and solve.
Inside the root: 2 × 14700 = 29400 , and 1.225 × 16 × 1.2 = 23.52 .
The division comes out suspiciously round. Take the square root last.