Question

A body covers 12m in 2nd sec. and 20m in 4th sec find what distance the body will cover in 4th sec after the 5th sec

Answer 1

the body will cover 54 m after the 4th second after the 5th second

Answer 2

Answer:

Explanation:

Given :

Case I:

let initial velocity = u m/s

distance=s=12m

Time =t=2sec

S=u+a(2t-1)/2

12=u+(2x2-1)/2

12=u+3a/2

2u+3a=24--------------(1)

Case II:

Time=t=4sec

distance =s=20m

20=u+a(2x4-1)/2

20=u+7a/2

2u+7a=40--------(2)

from 1 and 2:

2u+3a=24

2u+7a=40

-      -     -

***********

-4a=-16

a=4m/s2

substitute the value of a in equation 1 we get :

u=6m/s 

Case iii:

Now, distance covered in 4sec after 5second=distance covered in 9th sec-distance covered in 5 sec

=(6x9+1/24x9x9)-(6x5+1/2*4*5*5)

=54+162-(30+50)

=136m