Assignment 3:

6.5: How much of an automobile's tire wear off during one rotation?

In order to determine how much a tire wears off during one rotation, first the factors that causes excessive friction and damage to the tire is eliminated to simulate a hypothetical situation. Factors such as the weather (rain snow and ice), or terrain in which a car is driven adds on or diminishes the amount of wear it causes onto the tire. Hence taking the maximum amount of mileage there is in a tire which ranges from 25000-50000 miles according to http://www.wisegeek.com/how-long-do-tires-last.htm and dividing it by the mile of one rotation in an average sized tire (of a 4 passenger seat car) which has a diameter of 25" you would find out how much the tire wears in one rotation. 

Knowing the radius is 12.5" we convert it to miles which is 1.973 * 10 ^-4 and find the circumference which is the mileage in one rotation by multiplying by pie. 

Circumference= 6.198*10^-4

6.198*10^-4/50000=1.24 *10^-8 is the amount of wear during each rotation.

6.9: How high do letters need on an expressway sign need to be readable?

In this question a couple of factors need to be calculated, first the cone of vision of the driver, the size of the letters and the elevation of the sign itself. The signs showing direction on an expressway are located directly facing the driver therefore needs to be above ground. The cone of vision of a driver according tohttp://www.cbu.edu/~gmcginni/classes/CE%20318%20Highway%20Engineering/PowerPoint/Characteristics%20of%20the%20Driver,%20the%20Vehicle%20and%20Road.pdf

is 10-12 degrees again we will take the maximum value to see how high the sign needs to be placed with a 12degree cone of vision. Using the 250x250mm letter exit signs frequently seen on the expressways. Therefore the tan(12) is equivalent to the hieght of the sign over the distance the driver is from the sign. 

tan(12)=.213

a person eyesight is unlimited as we can see stars millions of miles away but using a person with 20/20 vision means that farthest away a human eye can see detail on an object is 20 ft (6m) using this as the distance you can solve for the height the sign needs to be in order for the driver to read it:

(6m)*(tan(12))=1.275m ~4.25 ft 

Cyber Security:

One of the “Great Challenges” that engineers are facing today is Cyber Security. With the rise of technology and the creation of the Internet, security has become a great issue due to the crimes that can be committed through cyberspace. A Computer has now become an intricate part of our daily life, from transportation system, to cellphones, especially with the advancement of technology calls for a better security as smart phones for example provide easier financial checking, and store many private information in one little piece of technology; however without better technology to provide better security the advancement that makes everyday life simpler can be equally used against you.

            The current method that people are relying on is creating a perimeter over the network that they use with firewalls and routers to block intruders from accessing their personal files. However this does not provide a good preventive measure, as firewalls can be unlocked and bypassed eventually. This “plug in method” only serves to hinder the crimes and breaches of security for a little while until another weakness is found in the security allowing intruders access to confidential information, or a total crash in the system can occur and completely wipe out any data stored in the hardware. Furthermore even if personal security isn’t an issue the Internet is a manner in which societally we trade information and communicate. The problems now are increased as interception of information can occur if the route in which the information is flowing is not secure. Monitoring, and altercation of information can cause great security breaches in the military and financial world.  

            Engineers today are trying to create ways to write security checkpoints into a program thus eliminating the need for external aid such as firewalls that can be easily breached; and new innovative methods for authentication is greatly needed.  Along with the help of social, and political aspects can cyber crimes be dealt with. Judicially the laws needs to be regulated and kept up to date with the evolving technology and the crimes committed as a result. Currently, Engineers are in the process of researching more methods in which can provide better security however as technology grows in one direction the intruders, viruses and ways in which they succeed in breaching the security get better as well. A need for cyber security is a global necessity as the power of the Internet and cyberspace grows hence calling forth the aid of everybody to make it happen.