Superman is flying 54.5 m/s when he sees
a train about to fall into a river 850 m
away. He must reach the train in 4.22 s.
What acceleration does he need?
(Unit = m/s^2)

An object weighs 40n in air, weighs 20n when submerged in water and 30n when submerged in a liquid of unknown density. what is the density of the liquid?

Match each vocabulary term to its definition. 1. electrons neutral subatomic particles found in the nucleus of the atom 2. neutron lowest energy position of an electron in an atom 3. photon the path of an electron around the nucleus of an atom 4. ground state negatively charged, subatomic particles 5. protons packet of energy of specific size 6. element substance with only one type of atom 7. orbital positively charged, subatomic particles found in the nucleus of the atom

This is a form of winter precipitation. it is frozen precipitation falling as ice pellets. snowflakes melt into raindrops as they pass through a thin layer of warmer air. the raindrops then refreeze into particles of ice when they fall into a layer of sub-freezing air near the surface of the earth. this precipitation is called a) hail. b) rain. c) sleet. d) snow.