Regina conducted an investigation to determine whether earthworms add nutrients to soil. She used two pots of soil. She added three earthworms to the first pot. She did not add any earthworms to the second pot, which was the control. Regina tested the nutrient levels of the soil in both pots after two weeks. What type of investigation is Regina conducting?

descriptive
comparative
experimental
procedural

Na food processing facility, a spherical container of inner radius r1 5 40 cm, outer radius r2 5 41 cm, and ther- mal conductivity k 5 1.5 w/m · k is used to store hot water and to keep it at 100°c at all times. to accomplish this, the outer surface of the container is wrapped with a 800-w electric strip heater and then insulated. the temperature of the inner surface of the container is observed to be nearly 120°c at all times. as- suming 10 percent of the heat generated in the heater is lost through the insulation, (a) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the container, (b) obtain a relation for the variation of temperature in the container material by solving the differential equation, and (c) evaluate the outer surface tempera- ture of the container. also determine how much water at 100°c this tank can supply steadily if the cold water enters at 20°c.

When a spring is compressed, the energy changes from kinetic to potential. which best describes what is causing this change? work power gravitational energy chemical energy

Why is it important always to use horizontal bars in unit fractions when performing unit conversions?