At what maximum speed can aircraft land on an 800 m long runway when braking with acceleration a1 = −2.7 m / s2, a2 = −5 m / s2?

The path for uniformly accelerated motion is determined by the formula:
S = (v ^ 2-v0 ^ 2) / 2a
Acceleration here, in our case, should be substituted with a “minus” sign, because we have braking, acceleration is negative because it is directed against the vector of the initial velocity.
From this formula, we express v0:
V0 = √2aS
V01 = √ (2 * 2.7 * 800) = 65.7 m / s
V02 = √ (2 * 5 * 800) = 89.4 m / s