ICAR AICE-JRF/SRF (PhD) — Agricultural Engineering subjects 38–43 · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersDesigning machines around the people who use them, and measuring the noise, vibration and work load they face.
In the exams: GATE AG Section 3 (ergonomics asked in all 8 papers 2019–26); ICAR AIEEA-PG Unit V; ICAR AICE subject 39 Unit 5; NCEES PE health and safety
ICAR AICE-JRF/SRF (PhD) — Farm Machinery and Power Engineering (subject 39, Unit 5)
Ergonomics and safety at PG depth: design of controls and seats from anthropometric data, workload assessment and acceptable workload as a share of VO2max, TCCW and PCW, rest allowance, posture analysis methods, ISO 2631 whole-body vibration assessment, noise exposure standards, accident causation models and ROPS test principles.
How our questions for ICAR AICE-JRF/SRF spread across the units of Human Engineering, Ergonomics & Safety. Difficulty: 5 easy, 36 medium, 20 hard.
| Work physiology: energy expenditure, heart rate and oxygen uptake | 14 | |
| Vibration: transmissibility and damping | 14 | |
| Anthropometry | 7 | |
| Dust and thermal stress | 7 | |
| Design of controls and seats | 5 | |
| Tools designed for women workers | 5 | |
| Noise: decibels and exposure | 3 | |
| Farm accidents and their causes | 3 | |
| Safety standards and ROPS | 3 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Using the regression EE (kJ/min) = 0.159 × HR − 8.72, the energy expenditure of a woman worker whose average working heart rate is 130 beats/min is
C. 11.95 kJ/min
EE = 0.159 × 130 − 8.72 = 20.67 − 8.72 = 11.95 kJ/min. Omitting the constant gives 20.67; adding it gives 29.39; 2.85 is the kcal/min value mislabelled as kJ/min.
Further reading: Varghese et al. regression used in Indian farm ergonomics
Resting heart rate is 72 beats/min. During a 30-minute trial the mean working heart rate is 118 beats/min, and the recovery beats above resting after work total 180. The physiological cost of work (PCW = TCCW / working time) is
B. 52 beats/min
CCW = (118 − 72) × 30 = 1380 beats; TCCW = CCW + CCR = 1380 + 180 = 1560 beats; PCW = 1560/30 = 52 beats/min. ΔHR (46) ignores recovery; 118 is the raw working heart rate; 1560 is TCCW, not per minute.
A pedal-operated thresher is driven with a mechanical power output of 60 W while the operator's energy expenditure is 21 kJ/min. The gross mechanical efficiency is about
A. 17.1%
21 kJ/min = 21 000/60 = 350 W; η = 60/350 = 17.1%. 28.6% divides 60 W by 210 instead of 350 (a slip in converting kJ/min to W); 2.9% is 60/21 = 2.86 with the units ignored; 4.8% divides 60 by 21 × 60 = 1260, multiplying by 60 instead of dividing. A value near 17% is plausible for pedalling.
Sustained static muscle contraction is fatiguing mainly because
D. the contracted muscle compresses its blood vessels and restricts blood flow
Static effort above about 15–20% of maximum restricts circulation, so metabolites accumulate and fatigue develops quickly even though whole-body oxygen uptake is modest.
Ten identical chaff cutters in a shed each produce 84 dB at a point. With all ten running, the level is
D. 94 dB
L = 84 + 10 log 10 = 94 dB. 87 is the two-source result; 104 uses 20 log 10; 840 is arithmetic addition.
A seat must isolate (transmit less than the input of) vibration at 5 Hz. Its natural frequency must be below about
C. 3.54 Hz
Isolation needs r = f/fn > √2, so fn < 5/√2 = 3.54 Hz. 5 Hz would be resonance; 7.07 Hz inverts the ratio; 2.5 Hz is sufficient but is not the limit.
A brush-cutter handle has frequency-weighted rms accelerations of 3, 2 and 4 m/s² in the three axes. The operator uses it for 2 hours a day. The daily hand-arm exposure A(8) is about
D. 2.69 m/s²
ahv = √(3² + 2² + 4²) = 5.385 m/s²; A(8) = 5.385 × √(2/8) = 2.69 m/s², above the EU action value of 2.5 m/s² but below the 5 m/s² limit. 5.39 ignores duration; 1.35 scales linearly; 4.50 adds the axes arithmetically.
In a seat test, the frequency-weighted acceleration is 0.45 m/s² on the seat and 0.60 m/s² on the floor below it. The SEAT value is
D. 75%, so the seat attenuates vibration
SEAT = seat/floor × 100 = 0.45/0.60 × 100 = 75%. Below 100% means attenuation. 133% inverts the ratio; 25% is the reduction, not the SEAT value.
A seat with stiffness 40000 N/m, effective mass 90 kg and damping coefficient 760 N·s/m has a damping ratio of about
B. 0.20
cc = 2√(km) = 2√(40000 × 90) = 3795 N·s/m; ζ = c/cc = 760/3795 = 0.200. Forgetting the factor 2 gives 0.40; the other options are formula slips. Putting the 2 inside the root, √(2km) = 2683, gives 0.28, and using 4√(km) gives 0.10.
A woman worker's VO2max is 1.8 L/min. Oxygen uptake is 0.75 L/min when weeding with a traditional tool and 0.62 L/min with a wheel hoe. Taking 35% of VO2max as the acceptable limit,
C. the wheel hoe (34.4%) is within the limit and the traditional tool (41.7%) is not
0.62/1.8 = 34.4% (< 35%) and 0.75/1.8 = 41.7% (> 35%). Only the wheel hoe can be sustained over a full day.
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