Objectives
1. Distinguish between an elastic material and an inelastic material.
2. Predict the stretch for an applied force, given the stretch produced by a
different force using Hook's law.
18.4 Compression and Tension
3. Explain why the center of a horizontal steel girder need not be as wide as the
top and bottom.
18.5 Scaling
4. Explain why making something larger by the same factor in all
dimensions changes its strength in relation to its weight.
19.1 Liquid Pressure
5. Describe what determines the pressure of a liquid at any point.
19.2 Buoyancy
6. Explain what causes a buoyant force on an immersed or submerged object.
19.3 Archimedes' Principle
7. Relate the buoyant force on an immersed or submerged object with the weight
of the fluid it displaces.
19.4 Does It Sink,or Does It Float?
8. Describe what determines whether an object will sink or float in a fluid.
19.5 Flotation
9. Given the weight of a floating object, determine the weight of fluuid it displaces.
19.6 Pascal's Principle
10. Describe how Pascal's principle can be applied to increase the force of a
fluid on a surface.
20.6 Buoyancy of Air
11. Explain what deterimnes whether an object will float in air.
20.7 Bernoulli's Principle
12. Describe the relation between teh speed of a fluid at any point and the
pressure at that point, for steady flow.
20.8 Applications of Bernoulli's Principle
13. Explain the principle source of lift on the wing of a bird or airplane.
Misconceptions
Note: The following statements are all FALSE!!!
1. What a structure is scaled up or down in size, its properties go up or down
in direct proportion.
2. Doubling the volume of an object means doubling the surface area, or
halving the volume means halving the surface area: Surface area and
volume scale up or down in direct proportion.
3. An animal scaled up in exact proportion, like King Kong, would
be proportionally stronger.
4. Liquid pressure depends on the total weight of liquid present.
5. Immersed and submerged mean the same thing.
6. The buoyant force that acts on a submerged object equals the weight of
the object.
7. Heavy things sink in water, while light things float.
8. Whether something sinks or floats depends on its weight.
9. Air has no weight.
10. Things float in air for different reasons than things float in water.
11. The faster a fluid moves, teh greater is its pressure.
12. Atmospheric pressure is greater during a hurricane or tornado.