GGRB28H3 Lecture : lecture 2

102 views3 pages

rosemuskrat776

2 Nov 2010

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

L02 - from colonialism to market triumphalism: relation between wealth and health. Access to food security enhances well being. Access to drinkable safe water, sanitation, sewage. Better access to technology (vaccines, antiviral drugs) Relationship between life expectancy & real income. Does not grow at the same rate/inclination. - up to a certain point (around per capital gdp), increasing national income contributes to improving health - increases slower afterwards. - countries at similar levels of national income can have different life expectancies. Micro/macro factors and influences that cannot be controlled. A 5% increase in income 1% reduction in infant mortality. Correlation in public spending on health - more spent, higher reduction in mortality. Falling fertility: uk, ireland - growing workforce: uk, ireland, asia. women are more readily available to work. Kenya tea pickers - people who are hiv- were able to work longer. People retire later - save for retirement more investment & wealth.

Related Questions

What is the relationship between the current through a resistor andthe potential difference (Voltage) across the resistor if theresister is made of ohmic material, Draw a graph of voltage versuscurrent for the resistor. How is the slop relates to itsresistance.
Do you expect the increasing temperature to affect the resistanceof the bulb, if so, how? sketch a qualitative graph of voltageacross a light bulb versus current through the light bulb.

What are intermolecular forces? How do they differ from intramolecular forces? What are dipole-dipole forces? How do typical dipole-dipole forces differ from hydrogen bonding interaction? In what ways are they similar? What are London dispersion forces? How do typical London dispersion forces differ from dipole-dipole forces? In what ways are they similar?

Describe the relationship between molecular size and strength of London dispersion forces. Place the major types of intermolecular forces in order of increasing strength. Is there some overlap? That is, can the strongest London dispersion forces be greater than some dipole-dipole forces? Given an example of such an instance.

blushlion324

Materials fracture when the force per unit area, called STRESS,exceeds a critical value. In general, the critical stress dependson the direction as well as the magnitude of the force. Forexample, bones break differently when subjected to torsional(twisting) stress than when subjected to compressional (orsqueezing) stress. Let us consider compressional stress. Wet humanbone for 20-39 year olds has an ultimate compressive strength of ~16x104Ncm2 [8]. Consider a person who falls from a height to theground. Upon landing, the person's kinetic energy is converted towork. If the person decelerates over a distance h, we can estimatethe average force during the collision by

If a person lands stiff-legged on a hard surface and doesn'tbounce, the deceleration occurs over a very short distance, h ~ 1cm. Since the force is transmitted up the leg, the stress isgreatest where the cross-sectional area is least, i.e., the tibiajust above the ankle [8].
The following lists some different conditions that may occur duringlanding and physical explanations for why they make bone fracturefrom a fall more or less likely [8]:

(a) bounce [more likely. The impulse is twice as large for anelastic collision as for an inelastic collision.]
(b) bent knees [less likely. Bending the knees increases the timeand distance over which deceleration occurs, which reduces theforce.]
(c) landing in loose earth or sand [less likely. This increases hwhich reduces F.]
(d) turning the body to land on the side [less likely. Thisincreases h. It also distributes the force widely over the body(increases A), thereby reducing the stress.]

So, why can a properly executed karate kick break a concrete blockwithout fracturing bones [16]? First, bone is a very strongmaterial. Its ultimate compressive strength is approximately 40times larger than concrete. Second, contact is made with the edgeof the foot. This concentrates the force into a small area of thetarget and reduces the likelihood of bending a bone to the point offracture. Third, the collision with the target is essentiallyinelastic and extends over several milliseconds, so the peak force,though large, does not exceed the strength of the bone. If A(cross-sectional area of the tibia) ~ 3.3 cm2, compute how far a 69kg person can fall and land stiff-legged on both legs withoutbreaking a bone. Assume F is split evenly between two legs. (Hint:F<or =2(theta)A )

GGRB28H3 Lecture : lecture 2

Document Summary

Get access

Related Documents

ECON 440 Lecture Notes - Lecture 4: Pasteurization, Cardiovascular Disease, Hand Washing

SOCI 365 Lecture 4: Lec 4

GEOG 106 Lecture Notes - Lecture 18: Human Genome Project, Bioprospecting, Pharmacogenomics

Related Questions