If an object travels 100 m in 5 seconds, how fast is it going on average?

Which best represents the law of conservation of mass ?

Where is the potential energy throughout the loading, cocking, and releasing of the trebuchet?

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?