Question

A particle is projected with velocity of $u=30\hat{i}+40\hat{j}$. Its velocity after $2$ seconds is
Take $(g=10m/s^2)$

• A. $10\sqrt{13}m/s$
• B. $5m/s$
• C. $10\sqrt{12}m/s$
• D. $10m/s$

Answer 1

The correct option is A $10\sqrt{13}m/s$

$u=30\hat{i}+40\hat{j}$
$u_x=30m/s,u_y=40m/s$
After $t=2s$,
$v_x=30m/s$ (Since horizontal component of velocity remains constant during projectile.)
$v_y=u_y-gt$
$=40-10\times 2=20m/s$
$v=\sqrt{v_x^2+v_y^2}=\sqrt{{30}^2+{20}^2}=10\sqrt{13}m/s$