Scientists in a test lab are testing the hardness of a surface before constructing a building. calculations indicate that the entire structure would sink by a certain amount for every additional floor that is added. if the maximum permissible limit for depression of the structure is 20 centimeters, how many floors can be safely added to the building?

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Can you match these to the correct definition

The direction of the current in an alternating current circuit remains constant. is direct. changes repeatedly. changes randomly.