Two bullets are fired horizontally and simultaneously towards each other from roof tops of two buildings $100 \mathrm{~m}$ apart and of same height of $200 \mathrm{~m}$, with the same velocity of $25 \mathrm{~m} / \mathrm{s}$. When and where will the two bullets collide? $\left(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^{2}\right)$ (1) They will not collide (2) After $2 \mathrm{~s}$ at a height of $180 \mathrm{~m}$ (3) After $2 \mathrm{~s}$ at a height of $20 \mathrm{~m}$ (4) After $4 \mathrm{~s}$ at a height of $120 \mathrm{~m}$

Home » Two bullets are fired horizontally and simultaneously towards each other from roof tops of two buildings apart and of same height of , with the same velocity of . When and where will the two bullets collide? (1) They will not collide (2) After at a height of (3) After at a height of (4) After at a height of

Two bullets are fired horizontally and simultaneously towards each other from roof tops of two buildings $100 \mathrm{~m}$ apart and of same height of $200 \mathrm{~m}$ , with the same velocity of $25 \mathrm{~m} / \mathrm{s}$ . When and where will the two bullets collide? $\left(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^{2}\right)$ (1) They will not collide (2) After $2 \mathrm{~s}$ at a height of $180 \mathrm{~m}$ (3) After $2 \mathrm{~s}$ at a height of $20 \mathrm{~m}$ (4) After $4 \mathrm{~s}$ at a height of $120 \mathrm{~m}$

Physics | Physics

Two bullets are fired horizontally and simultaneously towards each other from roof tops of two buildings $100 \mathrm{~m}$ apart and of same height of $200 \mathrm{~m}$ , with the same velocity of $25 \mathrm{~m} / \mathrm{s}$ . When and where will the two bullets collide? $\left(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^{2}\right)$ (1) They will not collide (2) After $2 \mathrm{~s}$ at a height of $180 \mathrm{~m}$ (3) After $2 \mathrm{~s}$ at a height of $20 \mathrm{~m}$ (4) After $4 \mathrm{~s}$ at a height of $120 \mathrm{~m}$

Answer (2)
Sol.

Let bullets collide at time t
$\begin{array}{l} x_{1}+x_{2}=100 \mathrm{~m} \\ 25 t+25 t=100 \\ t=2 s \\ \begin{array}{r} y=\frac{1}{2} g t^{2}=\frac{1}{2} \times 10 \times 2^{2} \\ =20 m \\ h=200-20=180 \mathrm{~m} \end{array} \end{array}$
Hence bullets will collide after $2 \mathrm{~s}$ at height $180 \mathrm{~m}$ above the ground.