Why is it that the properties of pure substance do not vary from sample to sample

In automobile steering wheel is shown what is the ideal mechanical advantage blank? if the ama is eight what is the efficiency of the steering wheel?

Frank just graduated from eighth grade. assuming exactly four years from now he will graduate from high school how many seconds does he have until his high school graduation

Which of the following is part of the explanation or description of electromagnetic waves? (select all that apply) a. electrically charged molecules in a medium transfer their energy to nearby electrically charged molecules. b. a changing electric field causes a changing magnetic field. c. magnetic molecules in a medium transfer their energy to nearby magnetic molecules. d. a changing magnetic field causes a changing electric field.