Question

A particle starts from the origin at $t=0$ with a velocity of $5\hat{i}m/s$ and moves in the $x-y$ plane with a constant acceleration of $(4\hat{i}+2\hat{j})m/s^2$. At what time is the $y-$ coordinate of the particle $9m$?

• A. $t=5s$
• B. $t=2s$
• C. $t=4s$
• D. $t=3s$

Answer 1

The correct option is D $t=3s$

Given, initial velocity of the particle in $y-$ direction. $u_y=0$
And acceleration, $a_y=2m/s^2$
$y-$ coordinate of the particle, $y=9m$
$y=u_{y}t+\frac{1}{2}{a}_y{t}^2$
$9=\frac{1}{2}\times 2\times t^2$
$t=3s$