Chapter 6: Internal Forces

(Press the TAB key to position the cursor at the beginning of the first blank and type what you believe completes the thought. Then press the TAB key for feedback and to move to the next blank. If you miss it, delete all of the word by positioning the cursor with the mouse and backspacing over all of the letters and try again. You should be able to complete this exercise without error before completing this chapter.)

A is a gas or liquid and has the essential features: 1) it assumes the shape of the container, and 2) it exerts no (perpendicular, shear?) forces when at rest. Shear forces are "sideways" forces as contrasted to perpendicular forces. When fluids exert forces on objects that they come in contact with, they exert forces at many, many points of contact. It is usually more useful to speak in terms of the force per unit area of contact. The force per unit area is called the . Pressure exerted by fluids is described by four simple rules: Rule 1: Each bit of fluid pushes outward, to any surface or boundary it contacts when the fluid is at rest. Rule 2: The pressure at a particular point inside a fluid is (the same, different?) in all directions. Rule 3: The pressure in a fluid (increases, decreases?) with depth. Rule 4: The pressure is the same at all point which are at the same depth. The pressure does not depend on the surface area of the fluid. The single force which replaces all contact forces on an object exerted by the fluid in which the object is immersed is called the force. Archimedes Principle: An object immersed in a fluid experiences an upward buoyant force whose strength is equal to the (volume, weight?) of the displaced fluid. A floating object at rest in a fluid is subject to a net force of zero. In such a case, the force (downward) equals the force (upwards). An iceberg floats in the water. If it snows and adds ice to the iceberg, the iceberg will (rise, sink?) . If the sun comes out and some of the iceberg melts, the remaining iceberg will (rise, sink?) . A small portion of a fluid is heated and expands. The volume of the heated fluid increases. According to Archimedes' Principle, the portion of fluid displaces (more, less?) of the surrounding fluid and will therefore (rise, sink?) . This motion is called a "convection current."

Click here to return to the Table of Contents