4. A uniform rod of length L and mass 2M rests over two supports A and B. A particle having mass, M is placed at the right end. Find the reactions at supports A and B. A 2L/3

A positron is an antimatter version of the electron, having exactly the same mass. When a positron and an electron meet, they annihilate, converting all of their mass into energy. (a) Find the energy released, assuming negligible kinetic energy before the annihilation. (b) If this energy is given to a proton in the form of kinetic energy, what is its velocity? (c) If this energy is given to another electron in the form of kinetic energy, what is its velocity?

Explain why a bound system should have less mass than its components. Why is this not observed traditionally, say, for a building made of bricks?

Each of the following reactions is missing a single particle. Identify the missing particle for each reaction. p+pn+? p+pp+0+? ?+p+? K+n0+? +e++ve+? (f)ve+pn+?

A particle physicist discovers a neutral particle with a mass of 2.02733 u that he assumes is two neutrons bound together. Find the binding energy. What is unreasonable about this result?

Suppose you are designing a proton decay experiment and you can detect 50 percent of the proton decays in a tank of water. (a) How many kilograms of water would you need to see one decay per month, assuming a lifetime of 1031 y? (b) How many cubic meters of water is this? (c) If the actual lifetime is 1033 y, how long would you have to wait on an average to see a single proton decay?

(a) Calculate the energy released in the a decay of 238U. (b) What fraction of the mass at a single 238U is destroyed in the decay? The mass of 234Th is 234.043593 u. (c) Although the fractional mass loss is laws for a single nucleus, it is difficult to observe for an entire macroscopic sample of uranium. Why is this?

(a) Write the decay equation for the decay of 235U. (b) What energy is released in this decay? The mass of the daughter nuclide is 231.036298 u. (c) Assuming the residual nucleus is formed in its ground state, how much energy goes to the particle?

(a) Verify from its quark composition that the particle could be an excited state of the proton. (b) There is a spread of about 100 MeV in the decay energy of the interpreted as uncertainty due to its short lifetime. What is its approximate lifetime? (c) Does its decay proceed via the strong or weak force?

(a) What is the kinetic energy in MeV of a ray that is traveling at 0.998c? This gives some idea of how energetic a ray must be to travel at nearly the same speed as a ray. (b) What is the velocity of the ray relative to the ray?