One end of spring is attached to a wall. The other end is attached to a movable block. If you pull the block so as to stretch the spring, is the work done by the spring on the block during the motion positive, negative, or zero

Madison lives near the ocean. she’s formed a hypothesis that increased concentrations of salt in the air speeds the corrosion of certain metals. if madison plans to test this hypothesis, she will have to deal with the following variables in her experiment: dependent variable: independent variable: one possible confounding variable: