Question

Time of flight of an object projected with $20m/s$ if velocity at maximum height is $12m/s$ is

• A. $1.6s$
• B. $3.2s$
• C. $4s$
• D. Data is insufficient

Answer 1

Answer: (B)

$3.2s$

Given,

$u=20m/s$

$H=12m$

$g=9.8m/s^2$

Maximum height in projectile motion,

$H=\frac{u^{2}si{n}^2\theta }{2g}$

$si{n}^2\theta =\frac{2gH}{u^2}$

$si{n}^2\theta =\frac{2\times 9.8\times 12}{20\times 20}$

$si{n}^2\theta =0.588$

$sin\theta =\sqrt{0.588}=0.7668$

Time of flight in projectile motion,

$T=\frac{2usin\theta }{g}$

$T=\frac{2\times 20\times 0.7668}{9.8}$

$T=3.2sec$

The correct option is B.