Determine which of these are action/reaction pairs

What does the term discrediting mean?

Name three different units of energy used to measure heat and describe what type of situations each is usually used.

Two forces produce equal torques on a door about the door hinge. the first force is applied at the midpoint of the door; the second force is applied at the doorknob. both forces are applied perpendicular to the door. which force has a greater magnitude?