GEOG 2075 Lecture : November 25 & 27 - Work .docx

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tealwildebeest525

14 Dec 2013

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Document Summary

Richard florida - the transformation of everyday life url. Required reading - connect electronically through library and read chapter 1. Some bemoan the passing of traditional social and cultural forms while others point to a rosy future based on new technology. Most see the transformation as one that"s done unwittingly some complaining that parts of society have imposed their values on the rest of us as others say our own inventions are turning around to shape us. We want society to change and that"s why it is. The driving force is the rise of human creativity a key factor in our economy & society. Working in different spheres in our lives, we value them highly and cultivate it more intensely. The creative impulse: attribute that distinguishes us as humans from other species. Our economy is powered by human creativity the ability to create meaningful new forms (websters dictionary)

Related Questions

At major league baseball games, it is commonplace to flash oil the scoreboard a speed for each pitch. This speed is determined with a radar gun aimed by an operator positioned behind home plate. The gun uses the Doppler shift of microwaves reflected from the baseball, an effect we will study in Chapter 39. The gun determines the speed at some particular point on the baseball's path, depending on when the operator pulls the trigger. Because the ball is subject to a drag force due to air proportional to the square of its speed given by R = kmʋ², it slows as it travels 18.3 m toward the plate according to the formula ʋ = ʋ_ie^-kx. Suppose the ball leaves the pitcher's hand at 90.0 mi/h = 40.2 m/s. Ignore its vertical motion. Use the calculation of R for baseballs from Example 6.11 to determine the speed of the pitch when the ball crosses the plate.

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The tangential force method involves finding the component of the applied force that is perpendicular to the displacement from the pivot point to where the force is applied. This perpendicular component of the force is called the tangential force.

(a) What is , the magnitude of the tangential force that acts on the pole due to the tension in the rope?

Express your answer in terms of

and

.

When using the tangential force method, you calculate the torque using the equation

$\tau = f_{\rm t} d$ ,

where

is the distance from the pivot to the point where the force is applied. The sign of the torque can be determined by checking which direction the tangential force would tend to cause the pole to rotate (where counterclockwise rotation implies positive torque).

(b) What is the magnitude of the torque

on the pole, about point A, due to the tension in the rope?

Express your answer in terms of

, and

The moment arm method involves finding the effective moment arm of the force. To do this, imagine a line parallel to the force, running through the point at which the force is applied, and extending off to infinity in either direction. You may shift the force vector anywhere you like along this line without changing the torque, provided you do not change the direction of the force vector as you shift it. It is generally most convenient to shift the force vector to a point where the displacement from it to the desired pivot point is perpendicular to its direction. This displacement is called the moment arm.

For example, consider the force due to tension acting on the pole. Shift the force vector to the left, so that it acts at a point directly above point A in the figure. The moment arm of the force is the distance between the pivot and the tail of the shifted force vector. The magnitude of the torque about the pivot is the product of the moment arm and force, and the sign of the torque is again determined by the sense of the rotation of the pole it would cause.