Question

A body is moving towards north with initial velocity
of 13 ms. It is subjected to a retardation of 2
ms-2 towards south. The distance travelled by it in
7th second is
(1) Zero
(3) 0.25 m
(2) 0.75 m
(4 0.5 m

Answer 1

Answer:

(1) Zero

Explanation:

Given,

Intial velocity of the body, u = 13 m/s

retardation, a = 2 $ms^{-2}$

As we all know retardation is negative acceleration of a body.

So, according to the law of motion,

distance travelled can be given by

$s\ =\ ut\ +\ \dfrac{1}{2}at^2$

where s = distance travelled

           u = initial velocity

           a = acceleration

           t = time taken

Hence, distance travelled in 7 s can be given by

$s_7\ =\ 13\times 7+\ \dfrac{1}{2}(-2)(7)^2$

        = 91 - 49

        = 42 m

distance travelled in 7 s can be given by

$s_7\ =\ 13\times 6+\ \dfrac{1}{2}(-2)(6)^2$

        = 78 - 36

        = 42 m

Hence, the distance travelled in 7th second can be given by

$s\ =\ s_7\ -\ s_6$

   = 42 - 42

   = 0

Hence, distance travelled in 7th second is 0 m.