Which two particles are found in the center of an atom?
electrons and ions
protons and neutrons
protons and electrons
electrons and neutrons

Protons and neutrons

Explanation:

According to the accepted theory of the structure of an atom ( note it isn't 100% accurate) the center of the atom, or the nucleus, contains the protons and neutrons. Around the nucleus you have electrons, which are located in electron shells and orbit the nucleus in nearly circular elliptical orbits. They orbit the nucleus because they are attracted to the protons in the nucleus (opposite charged particles attract one another.)

initial speed when it is dropped is 150 ft/s

now at the same moment the acceleration due to gravity is perpendicular to its velocity

so as we know that

now we have centripetal acceleration a = 32 ft/s^2 as its perpendicular to velocity

while tangential acceleration at the same moment will be zero

so

now radius of curvature is given as

so the radius of curvature just after it is dropped is 703.125 ft