Question:

Figure shows a body of mass m moving with a uniform speed $v$ along a circle of radius $r$. The change in velocity in going from $A$ to $B$ is:

Updated On: Jun 18, 2022
  • $ v\sqrt{2} $
  • $ v/\sqrt{2} $
  • $ v $
  • zero
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The Correct Option is A

Solution and Explanation

When a body rotates uniformly, then the direction of velocity changes continuously but its magnitude remains constant.
Also, direction of velocity is perpendicular to direction of motion.
$\therefore \vec{v}_{A}=\hat{j} \vec{v}$
$\vec{v}_{B}=-\hat{i} \vec{v}$
Change in velocity
$\Delta \vec{v}=\vec{v}_{B}-\vec{v}_{A}$
$=-\hat{i} \vec{v}-\hat{j} \vec{v}$
Magnitude of change in velocity is
$=|-\hat{i} \vec{v}-\hat{j} \vec{v}|$
$=\sqrt{v^{2}+v^{2}}=v \sqrt{2}$
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Concepts Used:

Motion in a Plane

It is a vector quantity. A vector quantity is a quantity having both magnitude and direction. Speed is a scalar quantity and it is a quantity having a magnitude only. Motion in a plane is also known as motion in two dimensions. 

Equations of Plane Motion

The equations of motion in a straight line are:

v=u+at

s=ut+½ at2

v2-u2=2as

Where,

  • v = final velocity of the particle
  • u = initial velocity of the particle
  • s = displacement of the particle
  • a = acceleration of the particle
  • t = the time interval in which the particle is in consideration