Members of Pantip’s Wahkor science forum have discussed whether bullets fired into the air by soldiers during clashes with protesters can be dangerous.

Krungthep Thurakij website reported the discussion on 18 April. 

Seiki, who started the thread, carried out calculations with the help of a computer programme.  With no practical knowledge of real guns, he chose the M16 and 5.56 mm standard NATO ammunition in his calculations, due to the availability of information on the internet.

With the initial velocity of a bullet fired from an M16 being 930 m/s or 3,348 km/hr, he put gravitational and air frictional forces into the equation.  Distances, heights, time durations and final velocities of a bullet fired from an M16 held one meter above the ground at angles of 30, 45 and 60 degrees were calculated.

It was found that the bullet, in all cases, takes less than one minute to reach the ground, and can go more than 4 kilometres.

This means that bullets fired at Khok Wua on Ratchadamnoen Rd could hit people walking at Pin Klao, Wong Wian Yai, Siam Square, or Hua Lamphong.

The minimum final velocity of the bullet is about 100 m/s or 400 km/hr, which is quite different from army claims that falling bullets just make the head bleed as if hit by a marble.

http://www.thephysicsofhockey.com/documents/speed.pdf

There have been reports of the danger of falling bullets causing damage to property or even death.  For example, there was a report of the death of a child from a bullet falling into a swimming pool in Phetchaburi.  The shooting of guns with real bullets at the opening and closing ceremonies of sports events has been prohibited in many countries, another member of the forum said.