Question

A jet needs to reach a speed of 180 knot before it take off is such plane spends 30s on runway estimate
1) it's acceleration
2) the minimum runway length

Answer 1

Initial speed (u) = 0 knots = 0 m/s

Final speed = 180 knots

1 knot = 0.514 m/s

Hence, 180 knots = 180 × 0.514 = 92.52 m/s

Final speed (v) = 92.52 m/s

Time taken (t) = 30 s

Let the acceleration be a.

$v = u+at$

$a = \frac{v-u}{t}$

$a= \frac{92.52}{30}$

1) a = 3.084 m/s^2

2) Let the length of the runway be s.

$s = ut +\frac{1}{2}at^2$

$s = 0 + \frac{1}{2} \times 3.084 \times 30^2$

s = 1387.8 m

Hence, the length of the runway should be 1387.8 m.