Question

An aeroplane lands with the velocity 80 m/s and comes to rest, after covering a runway of 1500 m. Calculate:
(i) retardation
(ii) time in which the aeroplane comes to rest​

Answer 1

Answer: a= -2.13m/s^2, t= 37.55

Here,

u = 80 m/s (initial velocity)

v = 0 (final velocity)

s = 1500 m

s= (distance covered before coming to rest, assuming straight line path.)

For calculating retardation,

$→ \: {v}^{2} = {u}^{2} + 2as$

$→0 = {80}^{2} + 2(a)(1500)$

$→6400 = - 3000a \\ →a = - \frac{6400}{3000} = - 2.13 \: m {s}^{ - 2}$

Here, a is negative ,

Indicating retardation.

For calculating time,

$→ V = u + at$

$→0 = 80 + ( - 2.13)t$

$→80 = ( 2.13)t$

$→t = 80 \div ( 2.13)$

$→ t = 37.55 \: sec$

Hence time taken to come in rest = 37.55 sec