Question

The trajectory of a projectile projected from origin is given by the equation y = x - $\frac{2x^2}{5}$ . The initial velocity of the projectile is

• A. $25\, ms^{-1}$
• B. $\frac{2}{5} ms^{-1}$
• C. $\frac{5}{2} ms^{-1}$
• D. $5 ms^{-1}$

Answer 1

Answer: (D)

$5 ms^{-1}$

Answer 2

$y=x -\frac{2x^{2}}{5}$ $tan \, \theta=1$ $\theta=45^{\circ}$ $\frac{g}{2u ^{2} cos ^{2}\theta}=\frac{2}{5}$ $\frac{10}{2u^{2} \frac{1}{2}}=\frac{2}{5}$ $u^{2}=\frac{50}{2}=25$ $u=5 \, ms^{-1}$