Evenwijdig en loodrecht Leerlingen moeten evenwijdige rechten, snijdende rechten en rechten die loodrecht op elkaar staan, herkennen en zelf kunnen tekenen.
Leerlingen moeten evenwijdige rechten, snijdende rechten en rechten die loodrecht op elkaar staan, herkennen en zelf kunnen tekenen.
See a Reversal
View a computer model simulation from NOVA Online that illustrates what happens during a magnetic field reversal, an infrequent occurrence that may be currently underway.
Quarks: Inside the Atom
This video segment adapted from NOVA shows how the particle accelerator helped physicists find parts of the atom even smaller than protons and neutrons.
When Did the First Americans Arrive?
In this video segment adapted from NOVA, recent archaeological evidence leads scientists to revise existing theories about human migrations into the Americas around the time of the last ice age.
Good Neighbors and Bad: Religious Differences on the Plains in the Early 20th century
The harmony of rural life is often romanticized, but differences among neighbors, whether ethnic, religious or political, could often lead to tension, especially as new groups emigrated west. Ezra and Dan Miller were born in a sod house in North Dakota but migrated with a group of Amish Mennonites to Montana. In this 1981 interview, conducted by Laurie Mercier for the Montana Historical Society, they described how local cowboys reacted to the influx of Amish farmers.
Gimme A Break! Mark Twain Lampoons the Horatio Alger Myth
The ideology of success--the notion that anyone could make it with enough hard work--was widely promoted in Gilded Age America. One of its most famous proponents was the author Horatio Alger, whose novels showed how poor boys could move from "rags to respectability" through "pluck and luck." Between the late 1860s and his death in 1899, Alger published more than 100 of these formulaic stories about poor boys who made good more often because of fortunate accidents than because of hard work and de
"We Sang Rock of Ages": Frances Willard Battles Alcohol in the late 19th century
Among the social movements joined and led by women in the late 19th century, including unionization and women's suffrage, none had either the widespread fervor or success enjoyed by the temperance movement. The Woman's Christian Temperance Union (WCTU), founded in 1873, drew widespread support from labor movements such as the Knights of Labor by linking the fight against liquor with the desire to protect home and family against the ravages of the new industrial order. Frances Willard was one of
"We Are Literally Slaves": An Early Twentieth-Century Black Nanny Sets the Record Straight
In folklore the black nursemaid was seen as a dutiful, self-sacrificing black woman who loved her white family and its children every bit as much as her own. Yet the popular images of the loyal, contented black nursemaid, or "mammy," were unfortunately far from the reality for the African-American women who worked in these homes. In 1912 the Independent printed this quasi-autobiographical account of servant life, as related by an African-American domestic worker, which dispelled the comforting "
The Bum as Con Artist: An Undercover Account of the Great Depression
Middle-class observers reacted to hoboes and tramps of the Great Depression with an array of responses, viewing them with suspicion, empathy, concern, fear, sometimes even a twinge of envy. For some, stolidly holding onto traditional values of work and success, the "bum" was suspect, potentially a con artist. Tom Kromer's "Pity the Poor Panhandler: $2 An Hour Is All He Gets" exemplified this stance, urging readers to resist the appeals of panhandlers and refer them to relief agencies, where prof
Slumming Among the Unemployed: William Wycoff Studies Joblessness in the 1890s
Even before the 1890s depression struck with devastating force in 1893, large numbers of jobless men and women competed in tight labor markets and faced homelessness. One of the best first-hand descriptions of "what it is to look for work and fail to find it" comes from political economist Walter Wycoff's two-volume study of The Workers: An Experiment in Reality, first published in 1899. Wycoff had abandoned his studies at Princeton to seek a more concrete appreciation of social problems. His re
This field exercise determines the susceptibility of different rocks to weathering, and, using the dates on the tombstones, estimates some weathering rates. Placing the field lab in context for use, this site describes the learning goals, teaching notes and materials, assessment recommendations, and provides links to other resources and references.
Determination of DNA Bases Chemistry: A Discovery-Based Experiment
The paper contains details of an electrochemistry lab where students are given the time to explore and design an experiment to identify the different DNA bases. The paper has a very useful compendium of literature relating to electrochemical techniques.
Flow Injection Analysis in the Undergraduate Laboratory
This paper titled, Flow Injection Analysis in the Undergraduate Laboratory, by Rocha and Nobrega was published in the Chemical Educator. It describes two basic experiments. One is the measurement of copper using PAR reagent as carrier in a single line FIA system. Increasing the reaction coil length results in double peaks. Refractive index effects are demonstrated in the two-line system by adding ethanol. The second experiment is the measurement of phosphate with the molybdenum blue reaction
Motion Mountain: The Free Physics Textbook
This site provides a free physics textbook that tells the story of how it became possible, after 2500 years of exploration, to answer such questions. The book is written for the curious: it is entertaining, surprising and challenging on every page. With little mathematics, starting from observations of everyday life, the text explores the most fascinating parts of mechanics, thermodynamics, special and general relativity, electrodynamics, quantum theory and modern attempts at unification. The es
Redes Inalámbricas en los Países en Desarrollo (Segunda edición en español)
The book is intended to be a comprehensive resource for technologists in the developing world, providing the information that they need to build real networks. By bringing this knowledge to the outer edges of the Internet, we hope to help jumpstart the construction of vital network infrastructure. Besides the topics included in the first edition, covering from basic radio physics and network design to equipment and troubleshooting, the second edition includes a new chapter dedicated to Voice ove
Types of Antennae
This illustrated guide is designed to help students recognize and learn the different types of antennae found on arthropods. The single Web page, which can be easily printed for use at field sites or in the lab, shows plumose (featherlike) pectinate (comblike) serrate (sawlike) moniliform (beadlike) filiform (threadlike) aristrate (with bristles) elbowed (with a bend) clubbed (the segments towards the end are larger).
Parts of an Insect (Grasshopper)
This illustrated guide to a grasshopper is designed to help students recognize and learn the body parts of an insect. The single Web page, which can be easily printed for use at field sites or in the lab, also includes a short description for the following labeled parts: head thorax antenna abdomen spiracles coxa trochanter femur tibia tarsus genitalia wings.
This illustrated guide to leaf types is designed to help students understand the differences between compound and simple leaves. This single Web page can be easily printed for use at field sites. Along with an explanation of both types, the guide includes a short description of these related terms: petiole, leaf blade, leaflet, and axillary buds.
Parts of a Spider: Dorsal View of a Male Spider
This illustrated guide (dorsal view) to a male spider is designed to help students recognize and learn its common and unique body parts. The single Web page, which can be easily printed for use at field sites or in the lab, also includes a short description for the following labeled parts: chelicera pedipalp anterior eye row posterior eye row cephalothorax (or prosoma) pedicel abdomen (or opisthosoma) spinnerets coxa trochanter femur patella tibia metatarsus tarsus.
Some Clues to Describing and Understanding Organisms
This online guide helps students focus their biodiversity research in the classroom, field, and lab. It includes general and specific questions to consider, designed to help students see the clues they might otherwise miss and give them the vocabulary to discuss their findings. General questions include "What might this clue indicate?" and "Does the organism always occur in the same 'zone'? "Plant-specific questions range from "If it's woody, is there one main trunk (trees), or are there several