Students in a science class want to design an investigation to determine if fertilizer added to soil affects the average height of a plant over time. Which items would the students need to complete this investigation?
A tape measure, graph paper, a plant, and soil samples with the same amount of fertilizer
A microscope, a beaker, a plant, and soil samples with the same amount of fertilizer
A computer, a stopwatch, a plant, and soil samples with different amounts of fertilizer
A ruler, a calculator, a plant, and soil samples with different amounts of fertilizer

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s.part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.