Chapter 1: Problem 25
Given \(\$ 10\) million, how would you spend the money as an engineer in a business venture for the betterment and improvement of society?
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Chapter 1: Problem 25
Given \(\$ 10\) million, how would you spend the money as an engineer in a business venture for the betterment and improvement of society?
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An incident occurred in which a cantilevered section of a walkway under demolition fell in a bagasse warehouse area at a sugar mill, resulting in the death of a worker positioned on top of the walkway. The incident walkway was constructed of two \(2.625\) in. by 10 in. steel C-channel main beams spaced three feet apart with metal floor grating welded to the top of the C-channel beams. The cantilevered walkway had welded-on hand rails and was approximately three \(\mathrm{ft}\) in width, \(11 \mathrm{ft}\) in length and located at a height of \(40 \mathrm{ft}\) from ground level. This section weighed more than \(800 \mathrm{lbs}\). The worker was positioned on the cantilevered portion of the walkway cutting through the floor grating of the walkway when the cantilevered walkway section unexpectedly gave way and fell to the area below. The demolition of the walkway left one section of the walkway cantilevered and supported by the metal floor grating and by an undersized weld. Demolition proceeded without an engineering study of the structural integrity of the bagasse walkway as well as an adequate plan for demolition. A proper engineering study of the structural integrity of the bagasse warehouse walkway as well as an adequate demolition plan in reasonable engineering probability would have prevented the accident. Search the OSHA regulation at http://www.osha.gov and review the sections 29 CFR 1926.501(a)(2) and 29 CFR 1926.850(a). Write a paragraph relating each section to the above incident and describe how following the regulations would have reduced the risk to employees.
An electric motor draws a current of 10 amperes (A) with a voltage of \(110 \mathrm{~V}\). The output shaft develops a torque of \(9.5 \mathrm{~N} \cdot \mathrm{m}\) and a rotational speed of \(1000 \mathrm{rpm}\). All operating data are constant with time. Determine (a) the electric power required by the motor and the power developed by the output shaft, each in kilowatts; (b) the net power input to the motor, in kilowatts; (c) the amount of energy transferred to the motor by electrical work and the amount of energy transferred out of the motor by the shaft in \(\mathrm{kW} \cdot \mathrm{h}\) and Btu, during \(2 \mathrm{~h}\) of operation.
A steel wire suspended vertically has a cross-sectional area of \(0.1 \mathrm{in}^{2}\) and an initial length of \(10 \mathrm{ft}\). A downward force applied to the end of the wire causes the wire to stretch. The force varies linearly with the length of the wire from zero initially to \(2500 \mathrm{lb}\) when the length has increased by \(0.01 \mathrm{ft}\). Determine (a) the normal stress, in \(\mathrm{lb} / \mathrm{in}^{2}\), at the end of the wire as a function of the length of the wire and (b) the work done in stretching the wire, in \(\mathrm{ft} \cdot \mathrm{lb}\).
Stairways-and mechanical engineers sometimes design stairways-have certain geometric requirements for their design, e.g., stairway steps shall be uniform with respect to rise and run. Review local and/or uniform building codes for stairways and steps and record the requirements for rise and run. Also address and answer the question, why are building codes such as those for stairways required?
Design a danger sign and a caution sign for a power press. For specifications search online at http://www.osha.gov for 29 CFR \(1910.145\) entitled Specifications for accident prevention signs and tags. Describe the difference between a danger sign and a caution sign. When is the signal word "Warning" used?
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