Question

An airplane touches down at 225 kmh-1 and stops after 2 minutes. Calculate

length of runway.​

Answer 1

Answer:

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Explanation:

Given:

Initial velocity of aeroplane = 225 km/hr

Time taken to stop = 2 minutes.

To find:

Acceleration and length of the runway

Formulas used:

Let u => initial velocity, v => final Velocity , a => acceleration ,t => time and s => distance

1. v = u + at

2. v² = u² + 2as

Conversion:

225 km = 225 × (5/18) = 62.5 m/s

and 2 minutes = 120 seconds.

Calculation:

v = u + at

=> at = v - u

=> a = (v-u)/t

=> a = (0 - 62.5) /120

=> a = - (62.5/120)

=> a = - 0.520 m/s²...........(1)

Putting value of "a" in eq (2)

v² = u² + 2as

=> 0² = (62.5)² + 2 × (-0.520) × s

=> 1.041 × s = 3906.25

=> s = 3752.4 metres = 3.752 km.

So final answer is :

Acceleration is -0.520 m/s² and

Length of runway = 3.752 km

Negative sign in acceleration denotes retardation.

Answer 2

Explanation:

Given:

Initial velocity of aeroplane = 225 km/hr

Time taken to stop = 2 minutes.

To find:

Acceleration and length of the runway

Formulas used:

Let u => initial velocity, v => final Velocity, a => acceleration,t => time and s => distance

1. v=u+at

2. v² = u² + 2as

Conversion:

225 km = 225 × (5/18) = 62.5 m/s and 2 minutes = 120 seconds.

Calculation:

V = u + at

=> at = v - u

=> a = (v-u)/t

=> a = (0 - 62.5) /120

=>a=-(62.5/120)

=> a = -0.520 m/s..............

Putting value of "a" in eq (2)

v² = u² + 2as

=> 0² = (62.5)² + 2 x (-0.520) × s

=> 1.041 x s = 3906.25

=> s = 3752.4 metres = 3.752 km.