The mass of an electron and its antiparticle, a positron, is 0.511 MeV/c2 . In order to produce an electron-positron pair, a gamma ray must have an energy larger than 1.022 MeV because __________

Fill in the blank(s) with correct word


of the equivalence of mass and energy

Physics & Space Science

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The lowest energy level in an atom is

a. the absolute zero temperature. b. the ground state. c. the ionization level. d. responsible for Doppler shifts. e. the energy level from which the Paschen series of hydrogen originates.

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Proportional Reasoning: Two cars are traveling at the same speed and hit the brakes at the same time. Car A decelerates (decreases its velocity) at twice the rate of car B. If car B takes time T to stop, how long does it take car A to stop?

A. 4T B. 2T C. T D. T /2 E. T/4

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A certain automobile tire has a volume of 0.0185 m3. If the absolute (or total) pressure in the tire is 500 kPa and the temperature is 298 K, how many molecules are there inside the tire? (R = 8.31 J/mol ? K, NA = 6.022 × 1023 molecules/mol)

A) 2.25 × 1023 molecules B) 2.25 × 1024 molecules C) 3.25 × 1023 molecules D) 3.25 × 1024 molecules E) 3.25 × 1025 molecules

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Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other

With time, charge gradually leaks off of both spheres. When each of the spheres has lost half its initial charge, the magnitude of the electrostatic force will be A) 1/4 F. B) 1/8 F. C) 1/2 F. D) 1/16 F.

Physics & Space Science