Estuaries are dynamic ecosystems where salt water and fresh water mix. Usually this happens as fresh water flows from a river to an ocean. When would you expect the concentration of salt in the estuary water to be LOWEST near the mouth of the river? A. when the river flow is low and the tide is low
B. when the river flow is high and the tide is low
C. when the river flow is low and the tide is high
D. when the river flow is high and the tide is high

Adding more pulleys to a system of pulleys needed to lift an object. a. increases the force b. decreases the force c. increases the amount of work d. decreases the amount of work

Acylinder with a movable piston contains 11.7 moles of a monatomic ideal gas at a pressure of 1.32×10^5 pa. the gas is initially at a temperature of 300 k. an electric heater adds 43200 j of energy into the gas while the piston moves in such a way that the pressure remains constant. cp=20.79 j k^−1 mol^−1 for a monatomic ideal gas, and that the number of gas molecules is equal to avogadro's number (6.022×10^23) times the number of moles of the gas. (a) what is the temperature of the gas after the energy is added? (b) what is the change in volume of the gas? (c) how much work is done by the gas during this process?

How many neutrons does element x if it’s atomic number is 28 and its mass number is 87