Question 1

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?

Accepted Answer

In 15 hours, this substance has decayed to 1/8 of its original mass. In other words, the substance has progressed through three half-lives (1/2 x 1/2 x 1/2 = 1/8). Thus, a single-half life for this substance is 5 hours.

Question 2

Which of the following species is classified as an electrolyte?

Accepted Answer

Electrolytes conduct electricity in aqueous solution, and are typically found in the form of ions. In the context of the question, Na⁺ is the only electrolyte.

Question 3

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

Accepted Answer

The delocalized "sea of electrons" model describes bonding in metals. Therefore, the only metal, copper, must display this type of bonding.

Question 4

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

Accepted Answer

Euler's Formula is used to determine the critical buckling load of a simply-supported column. Euler's Formula is expressed as follows: F_cr = EI?²/L² Where E = Young's modulus of the material used to construct the column I = cross-sectional area moment of inertia L = column length

Question 5

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

Accepted Answer

The hydraulic radius of a sewer refers to the ratio of the cross-sectional area of flow to the wetted perimeter. (The wetted perimeter is the portion of a cross-section's perimeter that is "wet.") The equation that describes the hydraulic radius of a channel, R_h, is expressed as follows: R_h = A (cross sectional area of flow) / P (wetted perimeter)

Question 6

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

Accepted Answer

The basic types of connections for beams, columns, trusses, and joists are pin, roller, and fixed. Roller connections provide only vertical support while allowing for free horizontal movement and rotation. Pin connections provide vertical and horizontal support and allow rotation. Fixed connections provide vertical and horizontal support and limit rotation (moment).

Question 7

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

Accepted Answer

When evaluating the progress of a project using the Earned Value Management approach, a project is considered profitable when the actual budget spent is less than or equal to the earned value. A project is considered to be over budget whenthe actual cost is greater than the earned value. A project is considered to be behind schedule when the budgeted cost of work performed is less than the budgeted cost of work scheduled.

Question 8

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

Accepted Answer

Phosphate is a polyatomic anion with the molecular formula PO?^3-, and magnesium typically takes an oxidation state of +2. The simplest way to balance these charges gives the correct molecular formula, Mg₃(PO?)₂.

Question 9

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

Accepted Answer

Footings are appropriate to use when foundation loads can be supported by shallow soils. Reinforced concrete footings are designed to handle the foundation loads and local soil characteristics. Deep foundations may be used when shallow soils are not able to support the foundation loads cost-effectively. Piles may be used when deep, competent soil or bedrock can be used to support the foundation loads.

Question 10

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?

Accepted Answer

For most proposed land development projects, pre- and post-development watershed drainage patterns are compared to determine if substantial hydrologic alterations will be made to the watershed's groundwater recharge, water regime, and area runoff. The drainage patterns reviewed include the surface and subsurface paths of water entering, crossing, and leaving the site. Additionally, areas where water is stored within the project site are also evaluated for pre- and post-construction conditions.

Question 11

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)

Accepted Answer

The composite C value for the given drainage area for a 10-year storm recurrence interval is 0.45. Solution: Calculate composite C by using the following equation: C = (C₁A ₁+ C₂A ₂+ C₃A₃) / (A ₁+ A ₂+ A₃) C = [(0.25 acres x 0.49) + (0.25 acres x 0.22) + (0.10 acres x 0.95)]/ (0.25+0.25+0.10) C = 0.45

Question 12

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?

Accepted Answer

Potential safety and/or operational issues associated with a bridge spanning a recently repaved roadway that now a vertical clearance of 4-inches less than posted includes all of the listed issues. Drivers of large vehicles depend on the posted clearance values to avoid collisions with the bridge structure. Collisions with oveR_head structures often lead to multiple crashes due to limitations on stopping site distances, design speeds, and traffic conditions. Traffic delays may result from oveR_head structure collisions, multiple vehicle crashes and repairs to the damaged structure.

Question 13

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

Accepted Answer

The cut construction method for earth retaining system is described as when walls are constructed from the top down to the base (top-down construction), concurrent with excavation operations. Fill construction refers to a method used to construct a wall from the base to the top (bottom-up construction). The "cut" and "fill" designations refer to the manner by which the wall is constructed, not the nature of the earthwork performed during the construction process.

Question 14

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

Accepted Answer

When drinking treating water, the presence of a poor taste or unpleasant odor, or the awareness of an ambient water temperature may indicate that there is a water quality problem within a finished water storage facility. Stale water within a storage facility promotes the growth of microorganisms that cause poor tastes or unpleasant odors and is often a result of water stored too long. Stagnant water will approach ambient temperatures, and may be a result of short-circuiting or accumulated sediment that impedes mixing within a storage unit.

Question 15

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?

Accepted Answer

The statement, "Sizing is based on the measured flow conditions" is not correct when considering the surface overflow rates of primary settling tanks. Typically, the primary settling tanks are sized based on the surface area calculations performed using 1) the design average flow conditions and 2) design peak hourly flow conditions. The larger surface area of the two is used to size the primary setting tank. Specific design requirements for primary settling tanks are set by state regulating agencies.

Question 16

Cathodic protection is used to control which of the following?

Accepted Answer

Cathodic protection is used to control corrosion. Corrosion is an electrochemical process in which an electrical current flows through a metallic substance, causing a chemical reaction that results in pitting and, ultimately, complete deterioration. Cathodic protection systems use the electrical properties of metallic substances to protect against the corrosion of metallic piping and structures by forcing an electrical interaction.
There are two main types of cathodic protection systems:
· Galvanic - uses a sacrificial anode, placed adjacent to the structure to be protected, that corrodes instead of the structure
· Impressed current - a current is applied to a structure from an adjacent anode

Question 17

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?

Accepted Answer

AASHTO assumes that the height of a driver's eye and the height of an object above pavement are 42 inches and 24 inches (respectively) when developing recommendations for minimum stopping sight distances. AASHTO's recommended distances are a conservative estimate of how long it will take a driver to perceive a situation exists that will require them to stop, apply the brakes, and come to a complete stop. The stopping site distance is an important safety consideration to assure that drivers have a continuous length of visible roadway.

Question 18

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

Accepted Answer

Air-entrainment was a significant concrete technology advancement made in the 1930s to provide relief from internal pressure. Entrained air provides tiny areas within concrete into which water can expand when it freezes. Air-entrained concrete is recommended when a concrete structure is exposed to freezing conditions and is achieved by adding surfactants to a concrete mix.

Question 19

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?

Accepted Answer

The total volume of the grit chamber is 2,079 ft³ is required to handle an average flow of 3 million gallons per day (mgd), with a peak flow ratio of 2.5 with a detention time of 3 minutes. Solution: Volume of grit chamber = Peak Flow x detention time Where, peak flow = average flow x peak flow ratio = 3 mgd x 2.5 = 7.5 mgd Given, 1 mgd = 1.54 ft³/seconds (sec) Volume = 7.5 mgd x 1.54 ft³/sec x 3 minutes x 60 sec/minute = 2,079 ft³

Question 20

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

Accepted Answer

The Rankine and Coulomb Theories are used to analyze active and passive lateral earth pressure. The two theories are similar; however, the Rankine Theory assumes there is no adhesion or friction between the wall and the soil, and lateral pressure is limited to vertical walls. The Coulomb Theory assumes that there is friction between the wall and the soil and that lateral pressure is not limited to vertical walls.

Quiz 1: Civil Engineering