Question

A force of 9.oN is applied to a body at rest on a smooth horizontal surface If the body has a mass of 18.0 kg and it moves in the direction if the force, find the work done in first four seconds and the forth second

Answer 1

Given,

Force (F) = 9 N
Mass (m) = 18 Kg

As we know that,

=> F = ma

=> 9 N = 18 Kg x a

=> 9/18 = a

=> a = 0.5 ms^-2


Now, have to find the Distance transversed in first four seconds.

=> S = ut + 1/2 at^2

=> S = 1/2 x 0.5 x 4 x 4 ( As, u = 0 ms^-1).

=> S = 4 m


Hence,

=> Work Done = Force x Distance

=> W = ( 9 x 4) N-m

=> W = 36 J


Again, If we have to find the Distance transversed in fourth second then we will apply a Formula :-


$S_{nth} = u + \dfrac{a}{2}(2n-1)$

$S_{nth} = \dfrac{0.5}{2}(2\times4-1)$

$S_{nth} = 0.25 \times(8-1)$

$S_{nth} = 0.25 \times 7$

$S_{nth} = 1.75 m$


Hence,

=> Work Done = Force x Distance(nth)

=> W = (9 x 1.75) N-m

=> W = 15.75 J