Stress Test
This quantity, defined as force per unit area, is measured in Pascals in SI units.
What is stress?
These two laws, named for a German physicist, state that the sum of currents entering a node is zero and the sum of voltages around a closed loop is zero.
What are Kirchoff's laws?
This dimensionless number represents the ratio of inertial forces to viscous forces in a fluid flow.
What is the Reynolds number?
This type of material failure occurs suddenly without significant plastic deformation, and is characteristic of ceramics and glass.
What is brittle fracture?
In the SI system, this base unit of force is equivalent to one kilogram-meter per second squared.
What is the Newton?
This Italian polymath sketched designs for flying machines, tanks, and bridges centuries before they were built, earning him the reputation as history's most famous engineer-artist.
Who is Leonardo da Vinci?
This dimensionless material property, typically between 0 and 0.5, relates the lateral strain to the axial strain in a uniaxially loaded member.
What is Poisson's ratio?
In a DC circuit, power dissipated by a resistor can be calculated as current squared times this quantity.
What is resistance?
This law states that the pressure of an ideal gas is inversely proportional to its volume at constant temperature.
What is Boyle's law?
In a standard tensile test, this point on the stress-strain curve marks the transition from elastic to plastic behavior.
What is the yield point (or yield strength)?
This dimensionless number, defined as the ratio of flow velocity to the speed of sound, determines whether a flow is subsonic or supersonic.
What is the Mach number?
This structure, completed in 1889 as a temporary exhibit for the World's Fair, was nearly torn down but was saved because of its usefulness as a radio antenna.
What is the Eiffel Tower?
A 10"kN" tensile load is applied to a rod with a cross-sectional area of 100"mm"^2. The normal stress in the rod is this value, in MPa.
What is 100"MPa"?
A 9"V" battery is connected across three 6Omega resistors in parallel. The total current drawn from the battery is this value, in amps.
What is 4.5"A". R_"eq"=2Omega, I=9/2=4.5
What flows steadily through a horizontal pipe that narrows from a diameter of 10"cm" to 5"cm". If the velocity in the wider section is 2"m"//"s", the velocity in the narrower section is this value, in "m"//"s".
What is 8"m"//"s"? A_1v_1=A_2v_2, area ratio is 4:1, so v_2=4xx2=8
This common crystal structure has an atomic packing factor of approximately 0.68 and a coordination number of 8. Iron at room temperature is a well-known example.
What is BCC (body-centered cubic)?
The universal gas constant R is approximately 8.314 in SI units. Those units are these.
What are "J"//("mol"*"K")?
Vulcanization, the process of adding sulfur to rubber to make it durable and elastic, is named after the Roman god of fire but was discovered accidentally by this American inventor in 1839.
Who is Charles Goodyear?
A steel bar (E=200"GPa", alpha=12xx10^-6//"ºC") is fixed at both ends and uniformly heated by 50°C. The compressive stress that develops in the bar is this value, in MPa.
What is 120"MPa"?
sigma=EalphaDeltaT=200xx10^3xx12xx10^-6xx50=120
A 1"k"Omega resistor is in series with a 100mu"F" capacitor and a 10"V" DC source. The time constant of this circuit is this value, with units.
What is 0.1 seconds?
tau=RC=1000xx100xx10^-6=0.1"s"
An ideal Carnot engine operates between a hot reservoir at 500"K" and a cold reservoir at 300"K". Its thermal efficiency is this value, as a percentage.
What is 40%?
eta=1-300/500=0.4
A steel alloy has a fracture toughness of 50"MPa"sqrt("m"). If a through-thickness edge crack of length 5"mm" is present, and assuming the geometric factor Y=1.12, the critical stress that will cause fast fracture is approximately this value, in MPa.
What is ~~356"MPa"?
sigma=K_"Ic"/(Ysqrt(pia))=50/(1.12xxsqrt(pixx0.005))~~356
One horsepower is approximately equal to this many watts.
What is 746"W"?
The Voyager 1 space probe, launched in 1977, is the farthest human-made object from Earth. It is still transmitting data using a radio transmitter with roughly this much power—about the same as a refrigerator light bulb.
What is ~23 watts? (accept ~20–25 W)
A state of plane stress has sigma_x=120"MPa", sigma_y=40"MPa", and tau_(xy)=30"MPa". The maximum in-plane principal stress is this value, in MPa.
What is 130"MPa"? sigma_"avg"=80, R=sqrt(40^2+30^2)=50, so sigma_1=80+50=130
A 120"V" (rms) household outlet supplies a purely resistive 1440"W" space heater. The peak current drawn by the heater is this value, in amps.
What is 12sqrt(2)approx17.0"A"? I_"rms"=1440/120=12"A", I_"peak"=12sqrt(2)
Air at 300"K" and 100"kPa" is compressed isentropically to 800"kPa". Using gamma=1.4, the temperature after compression is approximately this value, in Kelvin.
What is ~~543"K"?
T_2=300xx(800/100)^(0.4/1.4)=300xx8^(2/7)~~543
On an iron-carbon phase diagram, this reaction occurs at 727°C, where austenite transforms into a lamellar mixture of ferrite and cementite upon slow cooling.
What is the eutectoid reaction (forming pearlite)?
The Stefan-Boltzmann law gives radiated power as sigmaAT^4. A blackbody at 600"K" radiates approximately this many times more power per unit area than one at 300"K".
What is 16?
"ratio"=(600/300)^4=2^4=16
The Apollo Guidance Computer that landed humans on the Moon had approximately this much RAM—an amount dwarfed by a modern pocket calculator.
What is 4 kilobytes (4 KB)? (accept ~2–4 KB)