A ball is projected upwards from the top of the tower with a velocity 50 ms-1 making an angle 30° with the horizontal. The height of tower is 70 m. After how many seconds the ball will strike the ground?

Question

A ball is projected upwards from the top of the tower with a velocity 50 ms-1 making an angle 30° with the horizontal. The height of tower is 70 m. After how many seconds the ball will strike the ground? (A) 3 sec (B) 5 sec (C) 7 sec (D) 9 sec

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/0df474713a03361ba387677e38ce353b-.png" /> overline Y = overline v y t +(1/2) overline a y t 2 70=-(50 sin 30°) t+(1/2) × 10 × t2 70=-25 t+5 t2 or t2-5 t-14=0 ⇒ t=-2 sec or t=7 sec. (-ve time is not possible)

Q. A ball is projected upwards from the top of the tower with a velocity $50 m s^{- 1}$ making an angle $3 0^{\circ}$ with the horizontal. The height of tower is $70 m$ . After how many seconds the ball will strike the ground?

$3$ sec

$5$ sec

$7$ sec

$9$ sec

$\overline{Y} = \overline{v}_{y} t + \frac{1}{2} \overline{a}_{y} t^{2}$
$70 = - (50 sin 3 0^{\circ}) t + \frac{1}{2} \times 10 \times t^{2}$
$70 = - 25 t + 5 t^{2}$
or $t^{2} - 5 t - 14 = 0$
$\Rightarrow t = - 2 sec$
or $t = 7$ sec. (-ve time is not possible)

Q. A ball is projected upwards from the top of the tower with a velocity 50ms−1 making an angle 30∘ with the horizontal. The height of tower is 70m. After how many seconds the ball will strike the ground?

3 sec

5 sec

7 sec

9 sec