With what minimum horizontal velocity 'u', (in m/s) can a boy throw a rock at A so that it just clear the obstruction at B [ Take g =10 ms -2 ]

Question

With what minimum horizontal velocity 'u', (in m/s) can a boy throw a rock at A so that it just clear the obstruction at B [ Take g =10 ms -2 ] (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

-20=40 tan 0-(1/2) ( g × 402/ u 2 cos 2 0°) u 2=(1600/4)=400 u =20 m / s

Q. With what minimum horizontal velocity ' $u$ ', (in $m / s$ ) can a boy throw a rock at $A$ so that it just clear the obstruction at $B$
[ Take $g = 10 m s^{- 2}$ ]

$- 20 = 40 tan 0 - \frac{1}{2} \frac{g \times 4 0 ^{2}}{u ^{2} c o s ^{2} 0 ^{\circ}}$
$u^{2} = \frac{1600}{4} = 400$
$u = 20 m / s$

Q. With what minimum horizontal velocity 'u', (in m/s) can a boy throw a rock at A so that it just clear the obstruction at B [ Take g=10ms−2 ]

−20=40tan0−21​u2cos20∘g×402​ u2=41600​=400 u=20m/s

Q. With what minimum horizontal velocity ' $u$ ', (in $m / s$ ) can a boy throw a rock at $A$ so that it just clear the obstruction at $B$
[ Take $g = 10 m s^{- 2}$ ]

$- 20 = 40 tan 0 - \frac{1}{2} \frac{g \times 4 0 ^{2}}{u ^{2} c o s ^{2} 0 ^{\circ}}$
$u^{2} = \frac{1600}{4} = 400$
$u = 20 m / s$