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Mechanical Comprehension

Which of the following is not a modulus of elasticity?

stress modulus

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).

Mechanical Comprehension

Boyle's law defines the relationship between pressure and volume as:

\(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional". Expressed as a formula, that's \(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

General Science

Which of the following is not a base unit in the metric system?

degree Fahrenheit

The Fahrenheit scale is used for measuring temperature in the British system. The metric system uses the Celsius scale.

General Science

Which of the following is not part of the carbon cycle?

precipitation

The carbon cycle represents the ciruit of carbon through Earth's ecosystem. Carbon dioxide (CO₂) in the atmosphere is absorbed by plants through photosynthesis. Plants then die and release carbon back into the atmosphere during decomposition or are eaten by animals who breathe (respiration) the carbon into the atmosphere they exhale and produce waste which also releases carbon as it decays.

Automotive Information

What provides the power necessary to start a car?

battery

The battery supplies the power necessary to start the engine when the ignition switch is is turned on.

Math Knowledge

The dimensions of this cylinder are height (h) = 5 and radius (r) = 4. What is the surface area?

72π

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(4²) + 2π(4 x 5)
sa = 2π(16) + 2π(20)
sa = (2 x 16)π + (2 x 20)π
sa = 32π + 40π
sa = 72π

Mechanical Comprehension

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

45 lbs

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

Electronics Information

Which of the following statements about a capacitor is false?

it is safe to touch a capacitor with your hands as long as it is small

The purpose of a capacitor is to retain electric charge and it will do so even after its input voltage is removed. After the input voltage is removed, the capacitor will slowly discharge but, depending on the size and characteristics of the capacitor, discharging could take from a few minutes to a few years. So, it's never safe to touch a capacitor with your hands and you should make sure to discharge any capacitors in a circuit before working on it using an appropriately high-wattage resistor or a capacitor discharge tool.

Mechanical Comprehension

Which of the following represents how much two materials resist sliding across each other?

coefficient of friction

Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

General Science

Veins __________ blood at __________ pressure.

deoxygenated, low

Veins carry blood back to the heart from the body. While arteries are thick-walled because they carry oxygenated blood at high pressure, veins are comparatively thin-walled as they carry low-pressure deoxygenated blood. Like the heart, veins contain valves to prevent blood backflow.