Question

A gun fires a bullet at a speed of 140m/s.
If the bullet is to hit a target as the same level as the fun and at 1 km distance,the angle of projection may be

Answer 1

Since, range R = (u^2 sin2a)/g
And it is given that R= 1000 m
And u = 140m/s
Hence by putting all the values in the above formula ..
(140× 140 × sin2a)/10. = 1000
a= 1/2 sin^-1 (25/49)
This should be the angle of projection.
And formula for time of flight is
T= (2u sin a)/g
Maximim height H = {u^2 sin^2 (a)}/2g

I hope this answer might give some hint to your question...

Answer 2

We know equation of range:
i.e. R =     v²
            g × sin 2θ 
1000 =    (140)²
            9.8 × sin 2θ 
sin 2θ =    (140)²    
             1000 × 9.8
          = 19500
              9800
          = 0.5
2θ  = 30°
  θ  = 15°