Question

time of flight of an object projected with 20m/s if velocity at max height is 12m/s

Answer 1

an object is projected with speed 20m/s and velocity at maximum height is 12 m/s .

we know, at maximum height , only horizontal component exists. Let the object is projected $\theta$ angle with horizontal.

so, velocity of object at maximum height = $ucos\theta$

$\implies12=20cos\theta$

$cos\theta=\frac{3}{5}$

so, $sin\theta=\frac{4}{5}$

now, time of flight = $\frac{2usin\theta}{g}$
= (2 × 20 × 4/5)/10 = 3.2 sec