Agricultural and Biosystems Engineers Licensure Examination Engineering Properties of Agricultural Produce: practice questions

Question 1 · medium

Two seed lots are to be metered on an inclined plate. Lot X has aspect ratio W/L = 0.92 and Lot Y has W/L = 0.45. What behaviour should the designer expect?

1. Lot Y tends to roll down the plate while Lot X tends to slide, because elongated seeds present a smaller contact area
2. Both lots behave identically on the plate because aspect ratio affects only volume and not motion on a surface
3. Lot X tends to roll down the plate while Lot Y tends to slide, so the two need different plate angles and cell shapes
4. Lot X will not move at all on an inclined plate since round seeds have a higher coefficient of static friction

Question 2 · easy

A 0.5-litre test-weight measure filled by the standard procedure holds 0.392 kg of wheat. The test weight in kg/hL is

1. 784 kg/hL
2. 7.84 kg/hL
3. 78.4 kg/hL
4. 39.2 kg/hL

Question 3 · medium

A storage manager finds that the tonnage in a tall bin exceeds bin volume × bulk density measured with a standard poured-fill test. The best explanation is that

1. the standard poured-fill test overstates bulk density because it vibrates and packs the measuring container
2. grain in a tall bin is compacted under its own weight, so its in-bin bulk density exceeds the poured value
3. kernel density falls with depth in the bin, so lower layers contain more grain per cubic metre of space
4. the weighbridge records the moisture removed during storage as extra grain mass on the way in

Question 4 · easy

A sealed silo holds 100 m³ of grain bulk with a porosity of 40%. For a controlled-atmosphere treatment, what volume of intergranular air must be displaced to fill the voids once?

1. 40 m³
2. 60 m³
3. 100 m³
4. 140 m³

Question 5 · medium

In a winnower, the terminal velocities measured are 1.5–2.5 m/s for chaff and 7.5–9.5 m/s for sound wheat kernels. Which air velocity through the cleaning zone best separates them?

1. 1.5–2.0 m/s, equal to the lower end of the chaff range
2. 8–9 m/s, inside the terminal-velocity range of the grain
3. 12–14 m/s, above the terminal velocity of both fractions
4. 4–5 m/s, above the chaff range and well below the grain range

Question 6 · easy

Terminal velocity of grain kernels is measured in the laboratory by

1. timing kernels as they slide down a smooth inclined plane set at the angle of repose
2. raising an upward air stream until kernels float
3. dropping kernels through a water column and measuring the time to reach the bottom
4. measuring the pressure drop across a deep bed of kernels at known airflow

Question 7 · medium

Freshly harvested mangoes are placed in a water tank before grading, and some float. Which property is being used, and what do the floating fruit indicate?

1. Terminal velocity in air; the floaters have lower aerodynamic drag and are therefore the most mature fruit
2. Density relative to water; in many fruits the less dense floaters are immature or internally defective
3. Coefficient of friction; floaters have a waxier skin that repels water more strongly
4. Thermal diffusivity; floaters are warmer and less dense because they were picked in the sun

Question 8 · medium

A 200 g apple is dropped 0.30 m onto a hard surface. The energy available to cause bruising, E = m g h, is

1. 0.060 J
2. 0.589 J
3. 588.6 J
4. 5.89 J

Question 9 · medium

Under the United States regulation for thermally processed low-acid foods in hermetically sealed containers, a 'low-acid food' is one with

1. finished equilibrium pH less than 4.6 and water activity less than 0.85
2. finished equilibrium pH greater than 4.6 and water activity greater than 0.85
3. finished equilibrium pH greater than 7.0 and water activity greater than 0.95
4. finished equilibrium pH greater than 4.6 and water activity less than 0.60

Question 10 · medium

A storage manager uses the moisture content in equilibrium with about 65–70% relative humidity as the safe storage limit. Compared with wheat, the safe moisture content for groundnut kernels by this rule is

1. higher, because oil-rich kernels hold water much more strongly than the starch-rich kernels of cereals
2. the same, because safe storage moisture depends on relative humidity and not on composition
3. lower, because oil does not bind water, so the same humidity is reached at lower moisture content
4. higher, because groundnut kernels have a lower bulk density and so dry more slowly in store