From the top of a tower 20 m high, a ball is thrown horizontally. If the line joining the point of projection to the point where it hits the ground makes an angle of 45o with the horizontal, then the initial velocity of the ball is:

Question

From the top of a tower 20 m high, a ball is thrown horizontally. If the line joining the point of projection to the point where it hits the ground makes an angle of 45o with the horizontal, then the initial velocity of the ball is: (A) 10 ms-1 (B) 4 ms-1 (C) 15 ms-1 (D) 3 ms-1

Tardigrade Admin · Accepted Answer

Since angle with the horizontal is 45°, vertical height = range ⇒ 20 = u × 2 or u = 10 ms-1 (∵ t=√2h/g=√(2×20/10)=2 s)

Q. From the top of a tower 20 m high, a ball is thrown horizontally. If the line joining the point of projection to the point where it hits the ground makes an angle of $4 5^{o}$ with the horizontal, then the initial velocity of the ball is:

$10 m s^{- 1}$

$4 m s^{- 1}$

$15 m s^{- 1}$

$3 m s^{- 1}$

Since angle with the horizontal is $4 5^{\circ}$ ,

vertical height = range

$\Rightarrow 20 = u \times 2$ or $u = 10 m s^{- 1}$

$(∵ t = 2 h / g = \frac{2 \times 20}{10} = 2 s)$

Q. From the top of a tower 20 m high, a ball is thrown horizontally. If the line joining the point of projection to the point where it hits the ground makes an angle of 45o with the horizontal, then the initial velocity of the ball is:

10ms−1

4ms−1

15ms−1

3ms−1