Physics and Surfing :: physics surf surfing

When a wind begins to blow across a flat body of water ripples form almost immediately, then wavelets, and finally nearly fully developed waves, having almost definite wave lengths and shapes. Surface waves will also form, during calm wind, where opposing currents meet. This is known as current rips and can be dangerous for small or overloaded boats. A good estimate of the wind speed can be obtained by observing its effect on the water. For example, at 5 knots only small wavelets can be observed. A 10 knot wind speed will produce a few whitecaps. At 15 knots whitecaps can be seen up to 30% of the area. At 20 knots whitecaps can be seen up to 60% of the area. At 30 knots whitecaps and spray can be seen all over and foam from the breakers begins to form. At 40 knots streaks of foam can easily be seen. At 50 knots visibility is reduced and the sea begins to take on a white appearance from all the foam. Current directions and speed will greatly affect the areas covered by spray and breakers. Factors Affecting Wave Heights: 1. Wind. 2. Wind duration. 3. Length and width of wind fetch. (This is the distance over the water in which the wind blows in nearly the same direction.) 4. Depth of the water. 5. Direction and speed of the current. 6. Rate of precipitation. 7. Air temperature. 8. Amounts of flotsam, ice, or seaweed in the fetch area. 1. How high will the waves get? Maximum wave heights (in feet) will not get any higher than * the wind speed in knots. This is correct over 90% of the time. Note: Wave height begins to increase when the depth of the water is less than or equal to 1/4 of the wavelength because the wave starts to touch the sea floor. 2. What is the difference between waves and swells? Waves occur where the wind is blowing. Swells are waves that have moved away from the wind generating area and frequently give warnings of an approaching storm. 3. What is the significant wave height? Significant wave height (SWH) is the average height of 1/3 of the highest waves, or the height of the waves an observer is most likely to report. The significant wave height is used in the marine forecasts. Table 1.Wave heights in relationship to the significant wave height (SWH) Most frequent wave height .5 x SWH

Four Phases of Business Cycle Essay

Business Cycle (or Trade Cycle) is divided into the following four phases :- Prosperity Phase : Expansion or Boom or Upswing of economy. Recession Phase : from prosperity to recession (upper turning point). Depression Phase : Contraction or Downswing of economy. Recovery Phase : from depression to prosperity (lower turning Point). Diagram of Four Phases of Business Cycle The four phases of business cycles are shown in the following diagram :- The business cycle starts from a trough (lower point) and passes through a recovery phase followed by a period of expansion (upper turning point) and prosperity. After the peak point is reached there is a declining phase of recession followed by a depression. Again the business cycle continues similarly with ups and downs. Explanation of Four Phases of Business Cycle The four phases of a business cycle are briefly explained as follows :- 1. Prosperity Phase When there is an expansion of output, income, employment, prices and profits, there is also a rise in the standard of living. This period is termed as Prosperity phase. The features of prosperity are :- High level of output and trade. High level of effective demand. High level of income and employment. Rising interest rates. Inflation. Large expansion of bank credit. Overall business optimism. A high level of MEC (Marginal efficiency of capital) and investment. Due to full employment of resources, the level of production is Maximum and there is a rise in GNP (Gross National Product). Due to a high level ofeconomic activity, it causes a rise in prices and profits. There is an upswing in the economic activity and economy reaches its Peak. This is also called as a Boom Period. 2. Recession Phase The turning point from prosperity to depression is termed as Recession Phase. During a recession period, the economic activities slow down. When demand starts falling, the overproduction and future investment plans are also given up. There is a steady decline in the output, income, employment, prices and profits. The businessmen lose confidence and become pessimistic (Negative). It reduces investment. The banks and the people try to get greater liquidity, so credit also contracts. Expansion of business stops, stock market falls. Orders are cancelled and people start losing their jobs. The increase in unemployment causes a sharp decline in income and aggregate demand. Generally, recession lasts for a short period. 3. Depression Phase When there is a continuous decrease of output, income, employment, prices and profits, there is a fall in the standard of living and depression sets in. The features of depression are :- Fall in volume of output and trade. Fall in income and rise in unemployment. Decline in consumption and demand. Fall in interest rate. Deflation. Contraction of bank credit. Overall business pessimism. Fall in MEC (Marginal efficiency of capital) and investment. In depression, there is under-utilization of resources and fall in GNP (Gross National Product). The aggregate economic activity is at the lowest, causing a decline in prices and profits until the economy reaches its Trough (low point). 4. Recovery Phase The turning point from depression to expansion is termed as Recovery orRevival Phase. During the period of revival or recovery, there are expansions and rise in economic activities. When demand starts rising, production increases and this causes an increase in investment. There is a steady rise in output, income, employment, prices and profits. The businessmen gain confidence and become optimistic (Positive). This increases investments. The stimulation of investment brings about the revival or recovery of the economy. The banks expand credit, business expansion takes place and stock markets are activated. There is an increase in employment, production, income and aggregate demand, prices and profits start rising, and business expands. Revival slowly emerges into prosperity, and the business cycle is repeated. Thus we see that, during the expansionary or prosperity phase, there is inflation and during the contraction or depression phase, there is a deflation.

Essay The Territorial Sxpansion of the United States in...

The Territorial Sxpansion of the United States in the 1840’s Throughout 1815 to 1860, the USA changed faster than in the previous 200 years. It was seen as the land of opportunities and masses of Europeans migrated to the USA. Population figures doubled every 25 years. The number of states rised from 18 in 1815, to 30 by 1860. The agrarian society was soon replaced by a growing capitalist and commercial economy and there were advancements in transport and communication. Cities grew and the country was divided into three main sectors- agrarian west: mass immigration and industrial revolution in the Northeast and the slaveholding south. People moved westwards searching for new lives and†¦show more content†¦It was looked up as a shameful blot on the American record. Expansion of slavery was another important reason that led to territorial expansion. Eli Whitney’s invention of the Cotton Gin in 1793, made cotton production easier and more profitable, enabling it to spread from the Southeast into the old Indian lands of the west. The South was transformed by the expansion of cotton production. Due to the rise of textile industry in England, a huge demand for cotton was created. Cotton production rose from 3000 bales in 1790, to a 100,000 in 1801 and nearly 4 million in 1860. This caused the revitalization of slavery, which was a lucrative business, especially during the Civil War. The south’s economic dependence was mainly due to slavery. Illegal imports of slaves from Africa, led to a substantial rise in population. It wasn’t until 1794, when the first hard-surfaced road connected Philadelphia and Lancaster led to transport improvement and therefore a general improvement of communication. Without transport improvement, expansion would have taken a much slower path. Most turnpikes were financed and built privately and the road running across the Appalachians led thousands of pioneer families to settle westwards. Other forms of competition subsided the building of roads. After John Fitch had successfully demonstrated a paddle wheeler, it was Robert Fulton who made