What is the answer to this ?

Ageologist determines that a sample of a mineral can't be scratched by a steel nail but can be scratched by a masonry drill bit. based on this information, the sample mineral has to be softer than a. orthoclase. b. fluorite. c. apatite. d. corundum.

The number to the right of an element's symbol (ex. c-12) identifies the of an isotope.

Ajet plane is speeding down the runway during takeoff. air resistance is not negligible. identify the forces on the jet.