An electron and a positron are moving toward each other and each has speed 0.460 c in the lab frame. A. What is the kinetic energy of each particle? Ke-: J, Ke+ J
B. The e+ and e- meet head-on and annihilate. What is the energy of each photon that is produced? Eph: J
C. What is the wavelength of each photon? m

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

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According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?