Chapter 5 Physical Database Design and Performance 1) A requirement to begin designing physical files and databases is: A) normalized relations. B) definitions of each attribute. C) technology descriptions. D) all of the above.

only #2 represents an object at rest on a table.

in #1, there is no normal force due to the table; the object is accelerating downward.

in #3, the vertical forces are not balanced; the object is accelerating downward.

in #4, neither the vertical nor the horizontal forces are balanced. the object is accelerating upwards and to the right.