Fish tank water must be kept at at a particular pH level so the fish stay healthy. What is the best way you protect the water from becoming too acidic or too basic?

[A] Fill the tank with colored water
[B] Put pH paper on the tank
[C] Add acid to the water
[D] Add a buffer to the water

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

Consider an ordinary, helium-filled party balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.

If forces acting on an object are unbalanced. true or false