Greenwood press
Download 1.81 Mb. Pdf ko'rish
|
book-20600
82
PROPORTIONS The shadow produced on the ground at noon at Alexandria based on an angle of elevation of α degrees. Therefore the distance from Cyrene to Alexandria represented 7.2/360 of the earth’s circumference, since there are 360 degrees in a circle. Using the proportion, 7.2 degrees between cities 360 degrees in circle = 5000 stades between cities number of stades around earth , Eratosthenes determined that the distance around the earth is about 250,000 stades, or 139,750,000 feet. Since the cross section of the earth is approximately a circle, the radius can be determined by using the equation c = 2πr, comparing the circumference, c, to its radius, r. Substituting the value c = 139,750,000 feet and solving the equation will show that the radius of the earth is about 22,241,900 feet, or 4,214 miles. That’s only 6 percent off the actual distance of 3,963 miles! Movie screens are created to handle film with specific dimensions. Suppose the width of each film cell is 5.48 cm and the height is 2.30 cm. An ideal movie screen would show the entire picture without cropping out any of the sides. A small movie theater may leave a horizontal length of 7 meters, about 23 feet, to place its screen. In order to project the film perfectly on the screen, a proportion comparing the height and width needs to be used so that the correct height of the screen can be accurately determined. The height of the screen, h, is equal to ap- proximately 2.94 meters, or 9.66 feet, by solving the equation determined by the proportion h vertical meters on screen 2.30 vertical cm on film = 7 horizontal meters on screen 5.48 vertical cm on film . Proportions are used to predict the mass of a dinosaur with scaled models. Since a model is a miniature version of the actual dinosaur, paleontologists use the ratio length of actual dinosaur 3 length of model 3 = volume of actual dinosaur volume of model . This ratio is cubed, because volume is a three-dimensional concept, compared to a one-dimensional concept of length. For example, the volume of a cube is the Download 1.81 Mb. Do'stlaringiz bilan baham: |
Ma'lumotlar bazasi mualliflik huquqi bilan himoyalangan ©fayllar.org 2024
ma'muriyatiga murojaat qiling
ma'muriyatiga murojaat qiling