From the top of building 80 m high a ball is thrown horizontally which hits the ground at a distance. A line joining the top of the building to the joint where it hits the ground makes an angle ^{$45^{0}$} with the ground. Find its initial velocity.

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Solution

The correct option is B 20
$t a n 45 = \frac{80}{R} \Rightarrow R = 80 \Rightarrow u \sqrt{\frac{2 h}{g}} = 80 \Rightarrow u \sqrt{\frac{2 (80)}{10}} = 80 ∴ u = 20 m s^{- 1}$

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From the top of building 80 m high a ball is thrown horizontally which hits the ground at a distance. A line joining the top of the building to the joint where it hits the ground makes an angle 450 with the ground. Find its initial velocity.

The correct option is B 20 tan 45=80R⇒R=80⇒u√2hg=80⇒u√2(80)10=80∴u=20ms−1

From the top of building 80 m high a ball is thrown horizontally which hits the ground at a distance. A line joining the top of the building to the joint where it hits the ground makes an angle ^{$45^{0}$} with the ground. Find its initial velocity.

The correct option is B 20
$t a n 45 = \frac{80}{R} \Rightarrow R = 80 \Rightarrow u \sqrt{\frac{2 h}{g}} = 80 \Rightarrow u \sqrt{\frac{2 (80)}{10}} = 80 ∴ u = 20 m s^{- 1}$