Question:

A particle is moving on a circular path of radius $r$ with uniform speed $v$. What is the displacement of the particle after it has described an angle of $60^?$?

Updated On: Jul 5, 2022
  • $r\sqrt{2}$
  • $r\sqrt{3}$
  • $r$
  • $2r$
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The Correct Option is C

Solution and Explanation

According to cosine formula $cos\,60^{?}=\frac{r^{2}+r^{2}-x^{2}}{2r^{2}}$ $2r^{2}cos60^{?}=2r^{2}-x^{2}$ $x^{2}=2r^{2}-2r^{2}cos60^{?}$ $=2r^{2}\left[2sin^{2}\,30^{?}\right]=r^{2}$ $\therefore x=r$ Displacement $AB = x = r$
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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