Question

Plz answer this question...

Answer 1

Hey there !

Solution:

We know that,

Distance in Nth second = Distance covered in n - Distance in ( n - 1 ) sec

=> Sn = u + a/2 ( 2n - 1 )

Here acceleration is negative as the object is moving against gravity

Also we know that,

Distance in 5th second = Twice the distance in 6th second

=> S5 = 2 ( S6 )

S5 = u + ( -g/2 ) ( 2*5 - 1 )

=> S5 = u - 9g / 2

S6 = u + ( -g/2 ) ( 2*6 - 1 )

=> S6 = u - 11g / 2

Substituting that we get,

u - 9g/2 = 2 ( u - 11g/2 )

=> u - 9g/2 = 2u - 11g

=> 11g - 9g/2 = 2u - u

Substituting g = 10 m/s² we get,

=> 11 ( 10 ) - 9 ( 10 ) / 2 = u

=> 110 - 90/2 = u

=> 110 - 45 = u

=> u = 65 m/s

Hence the velocity of the projected sphere is 65 m/s.

Hope my answer helped !