4. when referring to the element phosphorus on the periodic table
osphorus on the periodic table, the number 15 represents
a. energy level.
b. atomic weight.
c. atomic number.
d number of atoms.

Two masses are connected by a rope that hangs over a pulley as shown below. the pulley is a uniform cylinder of radius 푅=0.381meters and mass 푀=3.1푘푔. initially 푚"is on the ground and 푚#rests 2.5 meters above the ground. if the system is released, use conservation of energy to determine the speed of 푚#just before it strikes the ground. assume the pulley bearing is frictionless.