Question

The distance covered by a particle thrown in a vertical plane along horizontal and vertical directions at any instance of time $t$ are $x=\sqrt{21}t$ meters and $y=2t-4t^2$ meters respectively. If all the units are $S.I$, find the initial velocity of the particle.

• A. $1m{s}^{-1}$
• B. $\sqrt{2}m{s}^{-1}$
• C. $1m{s}^{-1}$
• D. $5m{s}^{-1}$

Answer 1

The correct option is D $5m{s}^{-1}$

Comparing with equation of trajectory; $x=u_{x}t,y=u_{y}t-\frac{1}{2}g{t}^2$
$u_x=\sqrt{21};u_y=2u=\sqrt{u_x^2+u_y^2}$
$=\sqrt{21+4}$
$=5m{s}^{-1}$