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Has any other single invention changed history quite so much as explosives?

Has any other single invention changed history quite so much as explosives?. At 21.8 meters long, one of the world's biggest intercontinental ballistic missiles, the US Airforce LGM-118A Peacekeeper, is three times the length of a station wagon! . It’s just a BIG bullet!. BULLETS are made of .

JasminFlorian
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Has any other single invention changed history quite so much as explosives?

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  1. Has any other single invention changed history quite so much as explosives?

  2. At 21.8 meters long, one of the world's biggest intercontinental ballistic missiles, the US Airforce LGM-118A Peacekeeper, is three times the length of a station wagon! It’s just a BIG bullet!

  3. BULLETS are made of .. • Primer – like the fuse of a firework • Propellant – powers bullet through the air • Bullet – tapering metal cylinder

  4. Pulling the trigger … • A spring mechanism hammers a metal firing pin into the back end of the bullet, igniting the small explosive charge in the primer. • The primer then ignites the propellant. • Propellant chemicals burn, generate lots of gas very quickly. The gas shoots from the back of the bullet, increasing the pressure behind it, and forcing it down the gun barrel at extremely high speed (300 m/s is typical in a handgun).

  5. How bullets travel • Gun barrels have spiralling grooves cut into them that make bullets spin around very fast as they emerge. • A spinning bullet is like a gyroscope - if you try to tilt a gyroscope while it's spinning, it will try to resist whatever force you apply and, if you let go, it will soon tilt back the other way. • A bullet behaves in exactly the same way: once it's spinning, it follows a straighter path as it goes through the air, so it's harder to deflect and much more likely to reach its target.

  6. Inside the barrel

  7. The barrel of the gun has lands and grooves (grooves and ridges) cut in a spiral. The bullet moulds to these and starts to spin as it moves down the barrel. The bullet just continues to spin after it leaves the barrel. It is possible to calculate how fast a bullet will spin if you know the twist rate of the barrel and the velocity of the bullet.

  8. Can you work this out? • An AR15 has a twist rate of 1-in-8 i.e. for every eight inches the bullet travels down the barrel, the bullet is rotated once. It fires a .223 round at approx 2,800 feet per second. • The formula for number of revolutions is (bullet velocity x 720)/twist rate. HOW MANY REVOLUTIONS PER MINUTE IS THIS?

  9. Answer …. (2,800x720)/8 = 252,000 RPM!

  10. How much energy? The external ballistics of a bullet's path can be determined by several formulae, the simplest of which is: Kinetic Energy (KE) = 1/2 MV2

  11. Here the: Velocity (V) is given in feet/second (fps) Mass (M) is given in pounds

  12. The mass is derived from the weight (W) of the bullet in grains, divided by (7000 grains per pound times the acceleration of gravity).Acceleration due to gravity is 32 ft/sec².

  13. Now your turn! • Create a new formula to calculate KE using W etc. • Complete the worksheet • You may need to re-arrange this formula for parts of the table

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