Question:

A particle is projected from the origin in $xy$ plane. Acceleration of particle in $y$ direction is $\alpha$ . Its equation of path of projectile is $y = ax-bx^2$, then initial velocity of the particle is

Updated On: Jul 5, 2022
  • $\sqrt{\frac{\alpha}{2b}}$
  • $\sqrt{\frac{\alpha(1+a^2)}{2b}}$
  • $\sqrt{\frac{\alpha}{a^2}}$
  • $\sqrt{\frac{\alpha\,a^2}{b}}$
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The Correct Option is B

Solution and Explanation

y = ax-bx$^2$ $y = x$ tan $\theta - \frac{\alpha \,x^2}{2 u^2 \, \cos^2 \, \theta}$ $\because$ tan $\theta $ = a, $\frac{\alpha}{2u^2 \, \cos^2 \, \theta} = b;$ $\because \, u = \sqrt{\frac{\alpha (1 + a^2)}{2b}}$
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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