Question

The height $y$ and horizontal distance $x$ covered by a projectile in a time $t$ seconds are given by the equations $y=8t-{5t}^2$ and $x=6t$. If $x$ and $y$ are measured in metres, the velocity of projection is:

• A. $8{ms}^{-1}$
• B. $6{ms}^{-1}$
• C. $14{ms}^{-1}$
• D. $10{ms}^{-1}$

Answer 1

The correct option is D $10{ms}^{-1}$

$x=6t$

on differentiating with respect to t

$v_x=6$

$y=8t-5t^2$

$v_y=8-5t$

at t=0 $v_y=8$

$v^2=6^2+8^2={10}^2$

$v=10m/s$