A train approaches a stationary observer the velocity of train 1/20 of the velocity of sound a sharp blast is brown with the whistle of the engine at equal interval find the time interval between successive blasts as heard by an observer

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: