In a process called pair production, an energetic
gamma ray is converted into an electron and
a positron. it is not possible for a gamma ray to be
converted into two electrons because
(1) charge must be conserved
(2) momentum must be conserved
(3) mass-energy must be conserved
(4) baryon number must be conserved

the focus of lesson 1 is newton's first law of motion - sometimes referred to as the law of inertia. newton's first law of motion is often stated as. an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

explanation:

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered