How many scientists did it take to develop the atomic theory? please I need a number thanks

Mike walks 100 meter north, then walks 30 meters south. after this, he walks another 10 meters north. what is the magnitude of his total displacement during this walk,in meters?

Achemistry student needs of 40ml diethylamine for an experiment. by consulting the crc handbook of chemistry and physics, the student discovers that the density of diethylamine is 0.7 . calculate the mass of diethylamine the student should weigh out. round your answer to significant digits.

Which expression allows you to determine the mechanical advantage of an inclined plane? a. height of plane / input force b. length of plane / input force c. length of plane / height of plane d. height of plane / length of plane