An Electron-Positron Pair Traveling Towards Each Other with a Speed $\rarr$

question 49

Multiple Choice

An electron-positron pair traveling towards each other with a speed of v with respect to their center of mass,collide and annihilate according to e^- + e⁺ $\rarr$ $\gamma$ + $\gamma$ .An observer at rest with respect to the center of mass of the electron-positron pair,detects two photons each of wavelength 380 fm.What was the speed,v prior to the collision?

• A)0.976 c
• B)0.923 c
• C)0.950 c
• D)0.995 c
• E)0.988 c

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Definitions:

Gear Teeth

The protruding elements found on the circumference of a gear wheel, which interlock with those of another gear to transmit torque and motion.

Circular Thickness

The measurement of the thickness of a circular object or element, typically observed in cross-section.

Diametral Pitch

A value describing the ratio of the number of teeth of a gear to the diameter of the pitch circle, used in the design and specification of gears.

Circumference

The perimeter or boundary line of a circle, often measured to understand the size or to describe the distance around it.