Physics Review Sheet: Solids Part 2 Name _________________________ P ____
Do cd’s 18-1, 18-2 for hw before this class on 1/28/13
Concept Summary
Many solids are made of crystals.
 The atoms in a crystal have an orderly arrangement.
One property of solids is density, the amount of mass per unit volume.
 Density is related both to the masses of the atoms and the spacing between the atoms.
Another property of solids is elasticity.
 Elastic solids return to their original shape when a deforming force is applied and removed,
as long as they are not deformed beyond their elastic limit.
 By Hooke’s Law, stretch or compression is proportional to the applied force (within the
elastic limit).
 Inelastic materials remain distorted after the force is removed.
Scaling is the study of how size affects the relationships among weight, strength and surface area.
Important terms
Crystal
Density
Elastic
Elastic limit
Elasticity
Hooke’s law
Inelastic
Scaling
Specific gravity
Review Questions
1. How does the arrangement of atoms differ in a crystalline and a noncrystalline substance?
3. What evidence do we have for the visible crystal nature of some solids?
4. What happens to the density of a uniform piece of wood when you cut it in half?
5. Uranium is the heaviest atom found in nature. Why isn’t uranium metal the most dense
material?
6. Which has a greater density—a heavy bar of pure gold or a pure gold ring?
7. Does the mass of a loaf of bread change when you squeeze it? Does its volume change? Does
its density change?
9. What is the evidence for the claim that steel is elastic?
That putty is inelastic?
10. What is Hooke’s law?
What is the formula for spring potential energy?
11. What is an elastic limit?
12. A 2-kg mass stretches a spring 3 cm. What is the spring constant in N/m?
13. Is a steel beam slightly shorter when it stands vertically?
14. Where is the neutral layer in a horizontal beam that supports a load?
15. Why is the cross section of a metal beam I-shaped and not rectangular?
16. What is the weight—strength relationship in scaling?
17. If the linear dimensions of an object are doubled, how much does the total area increase?
…..How much does the volume increase?
18. True or False: As the volume of an object increases, its surface area also increases, but the ratio
of surface area to volume decreases? Explain.
19. Which will cool a drink faster—a 10gram ice cube or 10g of crushed ice?
20. Which has more skin—an elephant or a mouse?
Which has more skin per body weight—an
…….elephant or a mouse?
Think & Explain
1. Which has more volume—a kg of lead or a kg of aluminum?
2. Which has more weight—a liter of ice or a liter of water?
5. Metal beams are not rectangular but in the shape of an I. Why?
6. Show on a beam with a load where the compression & tension occurs.
7. If a model of a steel bridge is 1/100 of the real bridge, if the weight of the model is 50N, how
much would the real bridge weigh?
The model doesn’t sag but would the real bridge sag?
8. If you use a batch of cake batter for cupcakes instead of a cake and bake them for the time
suggested for baking a cake, what will be the result?
9. Explain, in terms of scaling, why it is an advantage that natives of the hot African desert tend to
be relatively tall and slender, and natives of the Arctic region tend to be short and stout. (Hint: A
piece of wire will cool faster when stretched out than when rolled into a ball.)
10. Animals lose heat through the surface areas of their skin. A small animal, such as a mouse, uses
a much larger proportion of its energy to keep warm than does a large animal, like an elephant.
Why is the rate of heat loss greater in a small animal than a larger one?