Possibly because they were frighted hope i helped (:
FN Normal force Perpendicular (i.e. normal) to the surface. Equal to whatever force is needed to prevent the object from falling through the floor. Use the FBD recipe to find FN . FT Tension In direction of the rope or string (away from the object).
Mass extinctions occur for many reasons. Changes in the environment might make it impossible for the local life to survive, diesease or drought might strike, or there might be a natural disaster. These extinctions make good divisions in geologic time because they are easy to locate over a wide area and mark a definitive change in the Earth's systems.
