Living things and geologic time: Cenozoic Mesozoic Paleozoic Precambrian

Arod of some material 0.20 m long elongates 0.20 mm on heating from 21 to 120°c. determine the value of the linear coefficient of thermal expansion [in (degrees c)^-1] for this material.

Achlorine atom has 17 protons and 18 neutrons. what is its mass number? what is its atomic number?

While carrying a heavy box up the stairs,you set the box on a step and rest. then you pick up the box and carry it to the top of the stairs. describe these actions in terms of balanced and unbalanced forces acting on the box.