Atomic Bombs

Whilst the commonly cited figure at Wikipedia is 64 Kg (141 lbs), the actual figure is 56 kilograms of 80% enriched Uranium 235, as cited in "The Last Mission, The Secret History of World War Two's Final Mission," published 2002 by Jim Smith and Malcolm McConnell giving the story of B-29 missions in the final days of WW2.

In contrast with:

http://en.wikipedia.org/wiki/Little_boy

The Quantity used was to ensure achieving natural critical mass, which falls in a range from 52 kilograms to 64 kilograms.

Various factors affect what determines natural critical mass such as:

Warhead temperature (cooler the better)

Density of fissile material

Geometry of the Warhead (spherical is smallest mass)

Isotope Purity

Neutron Flux & Uniformity

Use of Reflectors (ie containment of stray neutrons)

Of the 56 kilogram warhead of Little Boy which exploded over Hiroshima, only 780 grams or so exploded at the very heart of the Uranium sphere, or about 1-2% of the mass. That is because Neutron flux only attained criticality at the very heart of the sphere and not at the extremities where the Uranium 235 was wasted. When you increase efficiency of the Neutron Flux you require less fissile material. This is the key to shrinking a nuclear warhead.

In terms of the Hiroshima bomb however, 640 kilograms of un-enriched Uranium Oxide needed to be enriched to 80% 235U for a single weapon.

Uranium 235 is almost never used for nuclear weapons now. Pakistan still uses Uranium for it's warheads. Almost everywhere else now Plutonium is favoured for it's fail safe features.

Plutonium is harvested in a nuclear reactor by the radioactive bombardment of fuel which is enriched to 20% Uranium 235. The remaining Uranium 238 is converted to Neptunium 239 and then decays to Plutonium 239. The Plutonium is harvested by chemical separation from nuclear waste.

Only about 40 kilograms of un-enriched Uranium Oxide is required to obtain enough Plutonium via a heavy water nuclear reactor for a Plutonium weapon.

The US was by far the least helpful in ending WW2. If you want to know the truth Hitler actual invented the atomic bomb with a hoard of radioactive super weezles. The quickly dropped 2 atomic bobs on Japan because they were Germanys biggest threat. They planned to drop 5 on russia but the weezles refused to make more.

then quickly after Germany did this US took credit.

On August 6, 1945, Paul Tibbets flew an armed aircraft, named "Enola Gay", over Hiroshima, Japan, and dropped an atomic bomb, code-named "Little-Boy". On the ninth, Charles Sweeney flew an aircraft titled "Bockscar", over Nagasaki, Japan, and dropped "Fat Man".

Manhattan Project

Most people think so. Even the Japanese were grateful for the bomb because they were so tired of the war. President Truman believed the bomb will end the war sooner and save a lot of lives.

The US and Japan were at war, and Japan had refused to surrender. If the US invaded Japan, it was estimated that more than 1 million US service members would be killed, and several million Japanese would die. Japan was advised that the US had a new weapon, but would not surrender. After being bombed twice, they surrendered.

Wilson was President during the First World War 1914-1918, and he died in 1924. It was Harry Truman who was the President when the Atom Bomb was first used in 1945; it had been developed during the administration of Franklin D. Roosevelt and Truman authorized its use on Japan in 1945, during World War Two 1939-1945. Wilson created an organization of researchers and scientists (The National Research Council) and tasked them with working on such things as improvement of US weapons. Roosevelt and Truman too had a similar organizations of scientists and researchers (The National Defense Research Committee), and they were working on making military weapons more effective and the Office of Scientific Research and Development (OSRD) that helped develop the Atomic bomb

As I have said before, there was no "right" decision. What he did saved the lives of up to a million Allied troops who were scheduled to invade Japan. After the aggression on December 7, 1941, the United States firmly AND RIGHTLY decided that the Japanese military could not be allowed to survive the war and rebuild. Germany had not been adequately monitored following the end of WW1, and many remembered that the inadequate controls had led to WW2. That mistake could not happen again. The world agreed that Japan must unconditionally surrender, and if it required invasion of the mainland, so be it. Dropping the bombs ended the war without further loss of Allied life. It may not have been the "right" decision, but it was the lesser of the two evils. My father was scheduled to invade Japan and if you'll check your family history you'll probably find that you had an ancestor who was scheduled for that effort as well. Military leaders knew that it would be worse than D-Day. They knew that the loss of life would be terrible, on both sides. Japan refused to surrender, they were not receiving materials from outside Japan and their people were starving and dying from disease. Conventional bombing had destroyed homes, factories and infrastructure. Their war effort had destroyed their energy reserves. Most likley, more Japanese people would have died just from hunger and disease if the Allies had maintained the blockaid and conventional bombing. Remember that entire cities burned to the ground from conventional bombing, homes, schools, hospitals... we had the ability to keep that up almost indefinitely, and the emperor refused to surrender. He wanted to rebuild his military and take over the islands of the Pacific after learning from his previous mistakes. But the Allies also had learned from previous mistakes, and we did not allow him to rebuild. We did not start WW2, but we could not allow it to end without an acceptable surrender.

To prepare people for a possible atomic bomb attack

Stalin was terrified at the news of the new weapon. He couldn't proceed with his plans to acquired lands in the pacific. So the war far over but the cold war begun as well as the weapons race.

The purpose was to get Japan to surrender.

He didn’t. The Manhattan project was started several years before it was used. The bomb was all ready there when he took office.

some say that truman wanted to send a message to the soviet union

The bomb dropped on Hiroshima was called Fat Man. The bomb dropped on Nagasaki was called Little Boy.

Japan refused to surrender after the bombing of Hiroshima.

Harry S. Truman (23rd US President) succeeded to the office on April 12, 1945 when Franklin D. Roosevelt died.

Although both FDR and Truman had classified knowledge of the Manhattan Project, no decision could be made on the use of any A-bombs until they were shown to actually work. The first nuclear detonation came on July 16, 1945, two months after FDR died, and it was Truman's decision to actually employ them to force the surrender of Japan. Hiroshima was struck on August 6 and Nagasaki on August 9.

I suggest Richard Rhodes book The Making of the Atomic Bomb.

The critical mass of plutonium is lower, plutonium is not so expensive as highly enriched uranium, the technology to obtain plutonium is more simple than the isotopic separa-tion of uranium, etc.

The explosion of an atomic bomb (fission or fusion) is not a chemical reaction. The energy released comes from the destruction of matter (or rather the conversion of mass into energy) as Einstein's famous equation describes E=MC2.

In general, a fusion bomb (hydrogen bomb) is more powerful than a fission (atomic) bomb. Fusion bombs use an atomic bomb to begin the fusion reaction.

They called the atomic bomb pandora's box because it had many negative effects on a lot of people.
once opened, never closed. but that is true of all science/technology.

Yes you can use other items for a works bomb. A works bomb is just a small container filled with ingredients that when mixed together and ignited create a large explosion. Common items used in works bombs are:

• Gunpowder or black powder
• Fertilizer
• Fuel such as gasoline diesel or kerosene
• Matches or a fuse

You can also use other items such as sugar and potassium nitrate or even a mixture of baking soda and vinegar. However these items are not as powerful as the items listed above and the resulting explosion will be much smaller. It is important to remember that when making any type of works bomb safety should always come first.

yes AS WELL AS CELL DIVISION AND MORPHOGENESIS

the atomic bomb was not discovered, it was invented then built.

Because they bombed the American Flag, and killed lots of people.