FE Civil Engineering Exam Prep Flashcards

A 40.0 gram sample of a radioactive element decays to 5.0 grams in 15 hours. What is the half-life of this element?

Answer: 5 hours

Radioactive decay occurs at a constant half-life, meaning the amount of the substance halves over a fixed period. Starting with 40.0 grams, it decays to 20.0 grams after one half-life, then to 10.0 grams after a second half-life, and finally to 5.0 grams after a third half-life. Since this entire process took 15 hours, and it involved three half-lives, each half-life must be 15 hours / 3 = 5 hours.

Which of the following species is classified as an electrolyte?

Answer: Na+

An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, typically water, because it dissociates into ions. Na+ is a sodium ion, which is already in an ionic form and readily exists in solution, contributing to electrical conductivity. The other options (CH4, C6H12O6, N2, O3) are covalent compounds or elements that do not dissociate into ions in water and are therefore non-electrolytes.

Which of the following elements displays bonding characterized by a delocalized “sea of electrons?”

Answer: Copper

Copper is a metal, and metals are characterized by metallic bonding. In metallic bonding, valence electrons are delocalized and shared among a lattice of positively charged metal ions, forming a 'sea of electrons.' This allows for high electrical and thermal conductivity, which are characteristic properties of metals like copper.

Euler’s Formula is used to determine which of the following properties related to a simply-supported column?

Answer: Critical buckling load

Euler's Formula is a fundamental equation in structural engineering used to calculate the critical buckling load for slender columns. This load represents the maximum axial compressive force a column can withstand before it suddenly deflects laterally, or buckles. The formula considers the column's material properties, cross-sectional geometry, and effective length.

The hydraulic radius of a sewer refers to which of the following?

Answer: The ratio of the cross-sectional area of flow to the wetted perimeter

The hydraulic radius is a crucial geometric property used in open-channel flow calculations, such as those for sewers. It is defined as the ratio of the cross-sectional area of the fluid flow to the wetted perimeter, which is the portion of the channel perimeter in contact with the flowing fluid. This parameter is essential for determining flow velocity and discharge using equations like the Manning equation.

Which of the following is considered to be a basic connection types for beams, columns, trusses, and joists?

Answer: All of the above

Pin, roller, and fixed connections are the three fundamental types of supports or connections used in structural analysis for beams, columns, trusses, and joists. Each type imposes different constraints on translation and rotation, influencing how forces and moments are transferred. Understanding these basic connection types is essential for structural design and analysis.

When evaluating the progress of a project using the Earned Value Management approach, which of the following cases is a project considered profitable?

Answer: Actual budget spent is less than or equal to the earned value

In Earned Value Management (EVM), a project is considered profitable or under budget when the Actual Cost (AC) incurred is less than or equal to the Earned Value (EV). This indicates that the work accomplished (EV) has cost less than or equal to what was planned for that amount of work. Conversely, if AC exceeds EV, the project is over budget and less profitable.

Which of the following is the correct molecular formula for magnesium phosphate?

Answer: Mg3(PO4)2

To determine the correct molecular formula for magnesium phosphate, one must consider the charges of the constituent ions. Magnesium (Mg) is in Group 2, forming a Mg²⁺ ion, while the phosphate polyatomic ion is PO₄³⁻. To balance the charges, three Mg²⁺ ions (3 x +2 = +6) are needed for every two PO₄³⁻ ions (2 x -3 = -6), resulting in the formula Mg₃(PO₄)₂.

Which of the following best represents when footings are appropriate to use?

Answer: Foundation loads can be supported by shallow soils

Footings are a type of shallow foundation used when the soil near the ground surface has sufficient bearing capacity to support the structural loads. They distribute the concentrated loads from columns or walls over a larger area, reducing the pressure on the underlying soil. If shallow soils are not competent, deeper foundations like piles or caissons would be necessary.

For most proposed land development projects, pre- and post-development watershed drainage patterns are typically evaluated to determine if substantial hydrologic alterations are proposed that will result in which of the following?

Answer: All of the above

Land development projects often alter natural drainage patterns, leading to significant hydrologic changes. These alterations can increase impervious surfaces, which reduces groundwater recharge and increases surface runoff, potentially causing flooding and erosion. Additionally, changes in water flow can impact the water regime within sensitive resource areas, affecting ecosystems and water quality.

What is the composite C value for the following drainage area for a 10-year storm recurrence interval?Drainage area: 0.25 acres of residential lots with 40% imperviousness (C = 0.49) 0.25 acres of lawn with 0.95% slope with 0% imperviousness (C = 0.22) 0.10 acres of impervious pavement (C = 0.95)

Answer: 0.45

The composite C value is calculated by taking a weighted average of the C values for different land use types within a drainage area. For this problem, the calculation is: ((0.25 acres * 0.49) + (0.25 acres * 0.22) + (0.10 acres * 0.95)) / (0.25 + 0.25 + 0.10) = (0.1225 + 0.055 + 0.095) / 0.60 = 0.2725 / 0.60 = 0.454. Therefore, the composite C value is approximately 0.45.

Which of the following is a potential safety or operational issue associated with a bridge spanning a recently repaved roadway that now has a vertical clearance of 4-inches less than posted?

Answer: All of the above

A reduction in vertical clearance under a bridge, especially if unposted, poses several serious safety and operational issues. Over-height vehicles can collide with the bridge structure, causing damage to both the vehicle and the bridge. Such collisions can lead to multiple vehicle crashes due to debris or sudden stops, and the resulting accidents or bridge closures can cause significant traffic delays.

Which of the following best describes the cut construction method for earth retaining systems?

Answer: Walls are constructed from the top down to the base, concurrent with excavation operations

The 'cut' construction method for earth retaining systems, often referred to as top-down construction, involves building the retaining wall elements from the ground surface downwards. As excavation proceeds in stages, the wall is constructed concurrently, with each new section providing support for the next excavation lift. This method is particularly useful in urban areas or confined sites where open-cut excavation is not feasible.

When consuming drinking treated water, which of the following may be an indicator of water quality problems within a finished water storage facility?

Answer: All of the above

Poor taste, odor, and changes in water temperature can all be indicators of water quality problems within a finished water storage facility. Taste and odor issues often suggest the presence of microbial growth, chemical contamination, or stagnation. Significant temperature changes can also promote microbial activity or indicate issues with water circulation and quality degradation.

When considering the surface overflow rates of primary settling tanks in a typical municipal wastewater treatment plant, which of the following statements is not correct?

Answer: Sizing is based on measured flow conditions

While measured flow conditions are certainly considered, the statement 'Sizing is based on measured flow conditions' is not entirely correct as a sole determinant. Primary settling tanks are typically sized based on *design* flow rates (average and peak) and desired surface overflow rates, which are established criteria for effective solids removal, not solely on *measured* flow conditions which can fluctuate. The other options correctly describe considerations for primary settling tank design.

Cathodic protection is used to control which of the following?

Answer: Corrosion

Cathodic protection is an electrochemical technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. This method is commonly applied to pipelines, storage tanks, and other metallic structures exposed to corrosive environments, preventing the degradation of the material and extending its lifespan.

The Association of American State Highway and Transportation Officials (AASHTO) assumes that the height of a driver’s eye and the height of an object above pavement are which of the following (in inches) when developing recommendations for minimum stopping sight distances?

Answer: 42, 24

The American Association of State Highway and Transportation Officials (AASHTO) uses specific standard values for driver's eye height and object height when calculating minimum stopping sight distances. These values are 42 inches (3.5 feet) for the driver's eye height and 24 inches (2 feet) for the height of an object on the roadway. These parameters are critical for ensuring adequate visibility for drivers to safely stop their vehicles.

What significant concrete technology advancement was made in the 1930s to provide relief from internal pressure?

Answer: Air-entrainment

Air-entrainment was a significant concrete technology advancement in the 1930s, primarily developed to improve concrete's durability, especially in freeze-thaw conditions. By introducing microscopic air bubbles, it provides relief from internal pressure caused by freezing water, preventing cracking and scaling. This innovation greatly extended the lifespan of concrete structures in cold climates.

What is the total volume of a grit chamber designed to handle an average daily flow of 3 million gallons with a peak flow ratio of 2.5, and a detention time of 3 minutes?

Answer: 2,079 ft3

First, calculate the peak flow rate: 3 million gallons/day * 2.5 (peak ratio) = 7.5 million gallons/day. Convert this to ft³/min: (7.5 * 10^6 gallons/day) * (1 day / 1440 min) * (1 ft³ / 7.48 gallons) ≈ 695 ft³/min. Then, multiply by the detention time: 695 ft³/min * 3 min = 2085 ft³. The closest answer is 2,079 ft³.

Which of the following theories is used to analyze active and passive lateral earth pressure on retaining walls?

Answer: A. and B.

Both Rankine's theory and Coulomb's theory are widely used in geotechnical engineering to analyze active and passive lateral earth pressures on retaining walls. Rankine's theory is simpler, assuming a frictionless wall and a planar failure surface, while Coulomb's theory is more general, accounting for wall friction and a non-planar failure surface. Both provide methods to calculate the forces exerted by soil on retaining structures.