1. Wednesday(11/18): Conditions for Static Equilibrium. Elasticity and the

Calculation of a Modulus. HW: Read pages 362-370 and solve prob. 1, 5,11,

17, and 23 on pages 378-381.

2. Thursday(11/19): LAB on Inertial Balance. HW: Read pages 371-377

and solve prob.27, 39, and 33 on pages 381-2.

3. Friday(11/20): Post-lab Write-up. HW: Process lab data and write lab

report (due Tuesday).

4. Monday(11/23): Review Ch 12 - Static Equilibrium and Elasticity.

HW: Process lab data and write lab report (due Tuesday).

5. Tuesday(11/24): Click for TEST on Ch.12. HW: Go to website for notes

on Ch.13 - Universal Gravitation.

Website Notes for Ch.12: Static Equilibrium and Elasticity.

1. Part of this chapter is concerned with the conditions under which a rigid

object is in equilibrium.

2. The term equilibrium implies either that the object is at rest or that its

center of mass moves with constant velocity. We deal here with the former,

which are referred to as objects in static equilibrium.

3. One necessary condition for equilibrium is that the net force on an object

4. It is also good to still know the location of the center of mass, which is

5. If the net force on the particle is zero, the particle remains at rest (if

originally at rest) or moves with constant velocity (if originally in motion.)

6. The situation with real (extended) objects is more complex because

objects cannot be treated as particles.

7. In order for an extended object to be in static equilibrium, the net force

on it must be zero and it must have no tendency to rotate. This second

condition of equilibrium requires that the net torque about any origin be

8. In order to establish whether or not an object is in equilibrium, we must

know its size and shape, the forces acting on different parts of it, and the

points of application of the various forces.

9. The last sections of this chapter deals with the realistic situation of

objects that deform under load conditions. Such deformations are usually

elastic in nature and do not affect the conditions of equilibrium.

10. By elastic we mean that when the deforming forces are removed, the

object returns to its original shape. Several elastic constants are defined,

each corresponding to a different type of deformation.

11. The elastic properties of solids are described in terms of stress and

strain. Stress is a quantity that is proportional to the force causing a

deformation of the object. Stress = F/A . (Same as pressure.) Strain is a

measure of the degree of the resulting deformation. Strain = ΔL/L_o .

12. The elastic modulus of a material is the ratio of stress to strain for

that material. There is an elastic modulus for each of the three types of

deformation.

13. Young's modulus which measures resistance to change in length, is

given by Y = (F/A)/(ΔL/L_o) .

14. Shear modulus which measures resistance to relative motion of the

planes of a solid, is given by S = (F/A)/(Δx/h) .

15. Bulk modulus which measures the resistance to a change in volume,

is given by B = (ΔF/A)/(ΔV/V_o) .

View Slides          Try a Quiz         Try a Test

And still, we need these steps to solve any problem in Physics:

(i) read the problem and identify the given variables

(ii) determine what you are asked to solve for

(iii) find the correct vector formula to use

(iv) use Algebra, Trigonometry, and/or Calculus to isolate the unknown

(v) substitute-in the given information and simplify.

Check Homework.

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