Unit 2: Tractors and their control systems - Practice Quiz

1 Which type of tractor is designed mainly for working between rows of crops?

2 Which tractor cost remains payable even when the tractor is not being used?

3 Which of the following is a variable cost of tractor operation?

4 What is the main purpose of a tractor air cleaner?

5 Which air-cleaning device commonly uses a pool of oil to trap dust?

6 A clogged air cleaner most directly reduces the supply of what to the engine?

7 Which component stores fuel on a tractor?

8 What is the main function of a fuel filter?

9 In a diesel tractor engine, which component delivers fuel into the combustion chamber?

10 What is the main purpose of the engine cooling system?

11 Which cooling-system component transfers heat from the coolant to the surrounding air?

12 What does the thermostat control in a liquid-cooled tractor engine?

13 Which fluid property allows a tractor hydraulic system to transmit force?

14 Which hydraulic component converts fluid pressure into linear motion?

15 What is the function of a hydraulic pump in a tractor?

16 What is the primary purpose of engine lubrication?

17 Where is engine lubricating oil commonly stored in a wet-sump system?

18 What does an engine oil filter remove from lubricating oil?

19 What is the main function of a tractor transmission?

20 Which component allows the tractor operator to connect or disconnect engine power from the transmission?

21 A farmer needs a tractor mainly for inter-row cultivation in a tall cotton crop. Which tractor type is most suitable?

22 A tractor costs $900,000, has a salvage value of $150,000, and an economic life of 10 years. Using straight-line depreciation, what is its annual depreciation?

23 A tractor has fixed costs of $240,000 per year and variable costs of $600 per operating hour. If it is used for 600 hours annually, what is its total cost per hour?

24 A tractor operating in a dusty field shows black exhaust smoke and reduced power, while the fuel system is functioning normally. What should be checked first?

25 Why is a pre-cleaner fitted ahead of the main air filter on tractors used in very dusty conditions?

26 After a dry-type air filter element is replaced, the restriction indicator still shows excessive restriction. Which fault is most likely?

27 A diesel tractor runs unevenly immediately after its fuel filter is replaced. What is the most likely corrective action?

28 A diesel engine produces persistent black smoke when heavily loaded. Which fuel-system condition is a likely cause?

29 A tractor loses power after operating for an hour, but regains power soon after the fuel-tank cap is loosened. What is the probable fault?

30 A tractor overheats during heavy work, and its lower radiator hose remains cool while the engine is hot. Which component is most likely stuck closed?

31 Why does a pressurized cooling system permit an engine to operate at a higher coolant temperature without boiling?

32 A radiator core is clean and coolant level is correct, but the tractor overheats mainly at low engine speed. Which condition best explains this pattern?

33 A hydraulic cylinder has a piston area of and receives oil at . Ignoring losses, what force can it exert?

34 A three-point hitch lifts normally when cold but becomes slow after the hydraulic oil warms. Which fault is most likely?

35 An implement rises in jerks and the hydraulic pump makes a whining sound. The reservoir oil level is low. What is the most likely immediate cause?

36 An engine's oil-pressure warning lamp comes on at hot idle but goes off when speed increases. The oil level is correct. Which condition is most likely?

37 Why is a multigrade oil such as SAE 15W-40 often preferred for a tractor used across cold mornings and hot afternoons?

38 A tractor engine's oil level gradually rises and the oil smells strongly of diesel fuel. Which fault best explains the observation?

39 A tractor engine develops at . If the selected transmission ratio reduces axle speed to and losses are ignored, what axle torque is produced approximately?

40 A tractor slows under load while engine speed rises, and a burning smell comes from the clutch housing. What is the most likely fault?

41 Tractor A costs $48,000, has a salvage value of $12,000 after 8 years, annual insurance and housing costs of $1,200, and variable costs of $18/h. Tractor B costs $68,000, has a salvage value of $20,000 after 8 years, annual insurance and housing costs of $1,480, and variable costs of $13/h. Using straight-line depreciation and annual interest of 8% on average investment, at what annual use are their total costs equal?

42 A farm must perform sustained primary tillage on low-bearing-strength soil where drawbar pull, flotation, and low wheel slip are more important than transport speed or minimum turning radius. Which tractor classification is most appropriate?

43 A tractor will be used for 500 h/year. Ownership entails $9,000/year fixed cost, $16/h operating cost, and $2,000/year expected timeliness loss. Hiring costs $32/h and is expected to cause $6,000/year in timeliness loss. Which decision minimizes the annual relevant cost?

44 A two-stage tractor air cleaner receives 250 g/h of dust. The primary element removes 92% of entering dust, and the safety element removes 80% of the dust that reaches it. How much dust reaches the engine?

45 An engine's air-restriction indicator enters the red zone only at rated load. Replacing both filter elements does not change the reading, but temporarily removing a debris-covered precleaner inlet returns restriction to normal. Which fault best explains the observations?

46 A four-cylinder, four-stroke diesel operates at 1,800 rpm. Each cylinder receives of fuel per injection, and fuel density is . Neglecting return flow, what is the fuel delivery rate?

47 A mechanical governor has a no-load speed of 2,200 rpm and a full-load speed of 2,000 rpm at a fixed control setting. If the governor characteristic is linear, approximately what fraction of rated torque is being produced when speed stabilizes at 2,100 rpm?

48 After an injection-pump overhaul, a diesel exhibits difficult cold starting, black exhaust under load, reduced power, and unusually high exhaust temperature. Injector opening pressures and air supply are correct. Which adjustment error is most consistent with all symptoms?

49 A tractor engine transfers 45 kW of heat to its coolant. Coolant specific heat is , and its temperature rise through the engine is limited to . What minimum coolant mass-flow rate is required?

50 A cold tractor engine rapidly overheats after loading. Pump circulation has been independently verified, the radiator core is externally clean, and the radiator remains relatively cool while the cylinder-head temperature rises sharply. Which failure is most likely?

51 Two identical cooling systems use the same coolant and pressure-cap rating. One operates at sea level and the other at high altitude. Before either cap opens, which statement about coolant boiling temperature is correct?

52 A double-acting hydraulic cylinder has an 80 mm bore and a 45 mm rod. It operates at 16 MPa with a mechanical efficiency of 90%. Neglecting back pressure, what are its approximate extension and retraction forces?

53 A control valve is held against the end stop, causing 12 L/min of oil to pass continuously across an 18 MPa relief valve. Approximately how much hydraulic power is converted into heat?

54 During moldboard plowing with draft control engaged, the tractor enters a compacted patch and lower-link draft force rises above the selected value. What should a correctly adjusted system do first?

55 Oil pressure is normal immediately after a cold start but falls below specification at all engine speeds after the oil reaches operating temperature. The correct oil grade and oil level are confirmed, and the pressure gauge is accurate. Which condition is most likely?

56 A full-flow oil filter becomes severely restricted while the engine is operating at rated load. If the filter bypass valve functions correctly, what is the immediate system response?

57 Replacing the specified SAE 10W-30 oil with SAE 20W-50 raises indicated oil pressure, but bearing temperatures also rise during heavy operation. Which interpretation is technically sound?

58 A tractor engine runs at 2,100 rpm through an overall transmission reduction of 35:1. The driven-wheel rolling radius is 0.75 m, and wheel slip is 12%. What is the approximate actual travel speed?

59 An engine produces 140 N·m through a 4:1 gearbox and a 5:1 final drive. Gearbox efficiency is 95%, and final-drive efficiency is 92%. Neglecting differential losses, what torque reaches the axle?

60 A tractor uses a mechanical differential lock to escape a low-traction patch. It then reaches firm ground and must make a sharp turn. What action best protects the transmission and steering control?