The first step in the proton-proton chain produces an antielectron, or positron. What happens to the positron?

A) It slowly works its way to the Sun's surface, where it escapes into space.
B) It rapidly escapes from the Sun, traveling into space at nearly the speed of light.
C) It almost immediately annihilates with an electron, resulting in two gamma-ray photons.
D) It quickly meets an ordinary electron, forming an electron-positron pair that remains stable.
E) It joins with a nearby neutron to form a proton.


C) It almost immediately annihilates with an electron, resulting in two gamma-ray photons.

Physics & Space Science

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What will be an ideal response?

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One possible way to minimize its hazard is to pass it through a long pipe to allow it to decay inside the pipe until it can be safely released into the atmosphere. If the oxygen moves at a speed of 1.1 m/s in the pipe, how long must the pipe be for the sample to have decayed to 3.0% of its original activity just as it leaves the pipe? A) 8.0 m B) 680 m C) 7.0 m D) 2.0 m

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A piece of wood 350 mm × 350 mm and 15 mm thick conducts heat through its thickness under steady state conditions. The rate of heat flow is measured to be 14.0 watts when the temperature difference is 28 C°

Determine the coefficient of thermal conductivity for this wood A) 9.2 × 10-4 J/(m?s?C°) B) 270 J/(m?s?C°) C) 16 J/(m?s?C°) D) 0.061 J/(m?s?C°) E) 33 J/(m?s?C°)

Physics & Space Science