Which of these is an example of physical change? a. gasoline burning b. metal denting c. iron rusting d. silver tarnishing

I believe a physical change is one where the physical makeup of a substance is altered as opposed to a chemical change or molecular one which happens on a smaller scale. This would make me think that B. metal denting is accurate since all the other options are examples of chemical or molecular changes. A is an example of a liquid turning into a gas, which is a molecular change. The other two are chemical changes. Hope this is correct. 

The answer is metal denting

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.