Question

an aeroplane lands on a runway and comes to a stand still in 20 s, when the barking force acting on its wheel produces a radiation of 5 m/s². Find the initial velocity of the aeroplane during touch down in (i) (ii)km/h. [(i) 100 m/s (ii)360 km/h]​

Answer 1

Given:-

• Final velocity ,v = 0m/s
• Time taken ,t = 20 s
• Acceleration ,a = -5m/s ( opposite direction)

To Find:-

• Initial velocity ,u ?

Solution:-

⠀⠀⠀⠀⠀⠀⠀⠀⠀According to the Question

As it is given that the aeroplane lands on runway & stop after 20s. The retardation produced when force of brake are applied on it is 5m/s². we have to calculate the initial velocity of the aeroplane. Using 1st equation of motion .

• v = u + at

where,

• v denote final velocity
• u denote initial velocity
• a denote acceleration
• t denote time taken

Substitute the value we get

$:\implies$ 0 = u + (-5) × 20

$:\implies$ 0 = u - 100

$:\implies$ -u = -100

$:\implies$ u = 100m/s

• Hence, the initial velocity of the plane is 100m/s

So ,the required option is (i) 100m/s .

Answer 2

Given :-

An  aeroplane lands on a runway and comes to a stand still in 20 s, when the barking force acting on its wheel produces a radiation of 5 m/s².

To Find :-

Find the initial velocity of the aeroplane during touch down in (i) (ii)km/h.

Solution :-

We know that

v = u + at

0 = u + (-5)(20)

0 = u + -100

0 + 100 = u

100 = u

In km/h

100 × 18/5

1800/5

360 km/h