1. Chapter 9 Forces influence the motion and properties of fluids

2. Section 9.1 Forces & Buoyancy

3. Archimedes’ Principle Explains why some objects float in water while others sink; states that the buoyant force acting on an object equals the weight of the fluid displaced by the object; if the force of gravity is greater than the buoyant force, the object will sink, and vice versa.

4. Average Density The total mass of all of the substances that make up an object divided by the total volume of the object.

5. Balanced Forces The condition in which for every force acting on an object there is another force that is equal in strength and opposite in direction; the net force on the object is zero.

6. Buoyancy The upward force on objects submerged in (under the surface of) or floating on a fluid.

7. Buoyant Force Same as buoyancy.

8. Force Anything that causes a change in the motion of an object; a push or pull on an object.

9. Mass The amount of matter an object has.

10. Neutral Buoyancy The condition in which the forces acting on an object that is submerged in or floating on a fluid are balanced.

11. Unbalanced Forces The condition in which, for every force acting on an object, there is no equal and opposite force acting on it; the net force on an object is not zero.

12. Weight The measure of the force of gravity acting on the mass of an object.

13. Section 9.2 Pressure, Hydraulics, and Pneumatics

14. Compressibility The ability of a substance to be squeezed into a smaller volume or space.

15. Hydraulics The study of pressure in liquids.

16. Hydraulic Multiplication The ability to increase and transmit a force through a liquid from one point to another.

17. Hydraulic Systems Devices that transmit applied force through a liquid to move something else.

18. Incompressible The inability of a substance to be squeezed into a smaller volume or space; describes liquids and solids.

19. Pascal A unit used to measure pressure; 1 Pa is equal to 1 N/m 2

20. Pneumatic Systems Devices in which a gas is used to transmit force; force is exerted on a gas in an enclosed space to compress the gas and build up force that can be used elsewhere.

21. Pressure The force acting on a certain area of a surface.

22. Static Pressure Occurs when force is applied to an enclosed fluid (a fluid that is not moving).

23. Section 9.3 Relationships among Pressure, Volume, and Temperature of Gases

24. Controlled Variable A variable that is held constant (not allowed to change) during an experiment.