Question:

A body is travelling towards East with a speed of $9\, m / s$ and with an acceleration of $2\, m / s ^{2}$ acting along West on it. The displacement of the body during the $5^{\text {th }}$ second of its motion is

Updated On: Apr 29, 2024
  • 0.25 m
  • 0.5 m
  • 0.75 m
  • zero
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The Correct Option is D

Solution and Explanation

Displacement in the nth second is given by
$S_{n}=4+\frac{a}{2}(2 n-1)$
In this problem retardation is involved.
Thus, the equation becomes
$S_{n}=4-\frac{a}{2}(2 n-1)$
Given $u=9\, m / s , a=2\, m / s$
$n=5$
$\Rightarrow S_{5}=9-\frac{2}{2}(2 \times 5-1)$
$=9-9=0$
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Concepts Used:

Motion in a straight line

The motion in a straight line is an object changes its position with respect to its surroundings with time, then it is called in motion. It is a change in the position of an object over time. It is nothing but linear motion. 

Types of Linear Motion:

Linear motion is also known as the Rectilinear Motion which are of two types:

  1. Uniform linear motion with constant velocity or zero acceleration: If a body travels in a straight line by covering an equal amount of distance in an equal interval of time then it is said to have uniform motion.
  2. Non-Uniform linear motion with variable velocity or non-zero acceleration: Not like the uniform acceleration, the body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. The rate of change of its velocity changes at different points of time during its movement.