I will never forget that day. It was a day in BSF academy at Tekanpur. We were a batch of 96 officers being taken for an intensive training in arms. Of these, 20 of us engineers and IITians. Having studied projectile motion during our school days, we were quite keen to see it being demonstrated in case of. weapons, the man showing us the demo was using an AK-47 fitted with tracer bullets. As they were fired, we could actually see them, they would emit light. First of all the man fired at the center of the target 30 m away while firing horizontally. We could actually see the bullet moving in a parabolic path and hitting 2 cm below the target. ''You see. That is what I said. For accurate firing you need to aim not at the target but slightly above.'' `(g = 10 m//s^(2))`
What was the initila velocity of the bullet?

Options

A. `150 m//s`
B. `150 sqrt(10) m//s`
C. `150 sqrt(5) m//s`
D. `75 sqrt(2)`

Answer

B

Explanation

`y = x tan theta -(1)/(2)(gx^(2))/(u^(2)cos^(2)0^(@))`
`(2)/(100)=+(1)/(2)xx(10xx30^(2))/(u^(2))`
`u^(2)=250xx30^(2)`
`u = 150 sqrt(10)m//s`