Module 2 Physic Page 3

2.1. Mechanics – Statics.

Question Number. 1. An insulator has its electrons.
Option A. tightly bound.
Option B. loosely bound.
Option C. otally free from the atoms.
Correct Answer is. tightly bound.
Explanation. Aircraft Electricity & Electronics 5th edition TK Eismin.

Question Number. 2. The centre of gravity of an aircraft is adjusted by two weights, 10 kg and 5 ckg plaed 4m and 2 m aft of the c of g. To what position must a 20 kg weight be added to balance the c of g?.
Option A. 2.5m.
Option B. 4m.
Option C. 2m.
Correct Answer is. 2.5m.
Explanation. (10 * 4) + (5 * 2) = 20 x ? 40+10=20 x ? ? = 2.5m.

Question Number. 3. For the CGS system, the force is.
Option A. the 'N' which produces an acceration of 1 cm/s2 for a mass of gram.
Option B. the 'dyne' which produces an acceleration of 1cm/s2 for a mass of gram.
Option C. the 'pd1' which produces an acceleration of 1 cm/s2 for a mass of gram.
Correct Answer is. the 'dyne' which produces an acceleration of 1cm/ s2 for a mass of gram.
Explanation. NIL.

Question Number. 4. The quadrature component of a vector is.
Option A. 45° to the original.
Option B. 90° to the original.
Option C. 180° to the original.
Correct Answer is. 90° to the original.
Explanation. NIL.

Question Number. 5. 1 Newton is equal to.
Option A. 1 kilogram meter per second per second.
Option B. 1 kilogram of force.
Option C. 1 joule per second.
Correct Answer is. 1 kilogram meter per second per second.
Explanation. Remember Newtons 2nd law 'F=ma'. Well, 'm' is in kilograms, 'a' is in metres per second squared (or meters per second per second) so put the two together and 'F' is….

Question Number. 6. The SI unit of mass is the.
Option A. metre (m).
Option B. pound (lb).
Option C. kilogram (kg).
Correct Answer is. kilogram (kg).
Explanation. NIL.

Question Number. 7. A slug is a unit of.
Option A. speed.
Option B. mass.
Option C. weight.
Correct Answer is. mass.
Explanation. A very old unit of mass - equal to 14.6 kg.

Question Number. 8. If an object in air is submerged in a liquid or a gas its weight will.
Option A. increase.
Option B. decrease.
Option C. remain the same.
Correct Answer is. remain the same.
Explanation. thing that can change the weight of an object is the gravitational field it is in.

Question Number. 9. If a material is loaded excessively and is permanently deformed, it is said to be.
Option A. stretched.
Option B. stressed.
Option C. strained.
Correct Answer is. strained.
Explanation. Strain = extension / original length (Stress = force / area).

Question Number. 10. The SI unit of force is the.
Option A. Newton (N).
Option B. Metre (m).
Option C. Pascal (Pa).
Correct Answer is. Newton (N).
Explanation. NIL.

Question Number. 11. The formula for calculating stress is.
Option A. load divided by cross sectional area.
Option B. area divided by load.
Option C. load multiplied by cross sectional area.
Correct Answer is. load divided by cross sectional area.
Explanation. NIL.

Question Number. 12. Stress is given by.
Option A. force per unit area.
Option B. extension per original length.
Option C. force per original length.
Correct Answer is. force per unit area.
Explanation. NIL.

Question Number. 13. The force which opposes twisting deformation is.
Option A. torsion.
Option B. strain.
Option C. shear.
Correct Answer is. torsion.
Explanation. A torsional force opposes twisting.

Question Number. 14. A force perpendicular to a beam produces what type of stress?.
Option A. compressive.
Option B. shear.
Option C. tensile.
Correct Answer is. shear.
Explanation. perpendicular to a beam (such a s a man on a diving board) produces bending and shear stress. 

Question Number. 15. The extension of a spring can be determined using.
Option A. Charles' Law.
Option B. Newton's 2nd Law.
Option C. Hooke's Law.
Correct Answer is. Hooke's Law.
Explanation. Hooke's law is 'extension is proportional to force'.

Question Number. 16. When a steel bar is overstressed, what is the name of the point at which it does not return to its original form after the load is released?.
Option A. Ultimate point.
Option B. Yield point.
Option C. Young's modulus.
Correct Answer is. Yield point.
Explanation. NIL.

Question Number. 17. Two couples with magnitude F act against each other. The resultant will be.
Option A. -2F.
Option B. 2F.
Option C. 0.
Correct Answer is. 0.
Explanation. A 'couple' is 2 forces acting in the same rotational direction an equal distance from a pivot point (like turning a die holder). Two couples in opposition will cancel each other.

Question Number. 18. The height of mercury required to give 1 bar is.
Option A. 700 mm.
Option B. 1000 mm.
Option C. 760 mm.
Correct Answer is. 760 mm.
Explanation. 1 bar is almost atmospheric pressure.

Question Number. 19. A vessel has 25 ml of water which produces 10 kPa. If another 125 ml of water is added, what will be the pressure in the vessel?.
Option A. 40 kPa.
Option B. 50 kPa.
Option C. 60 kPa.
Correct Answer is. 60 kPa.
Explanation. pressure = density * gravity * height. 25ml + 125ml = 150ml or 6 times. So 6 * height = 6 * pressure.

Question Number. 20. Two hydraulic jacks with different diameters have the same fluid pressures entering at the same rate. They will extend at.
Option A. the same rate until the smaller jack becomes full.
Option B. the same rate.
Option C. different rates.
Correct Answer is. different rates.
Explanation. diameter will have the greater force. The 'trade-off' for this is that it will move slower.

Question Number. 21. What load can be lifted on jack B?.
Option A. 300N.
Option B. 200N.
Option C. 100N.
Correct Answer is. 100N.
Explanation. 10 times the area, then it can lift 10 times the load.

Question Number. 22. The most common method of expressing pressure is in.
Option A. inch pounds per square inch.
Option B. grams per square inch.
Option C. pounds per square inch.
Correct Answer is. pounds per square inch.
Explanation. Pressure is usually measured in Pounds per Square Inch (PSI).

Question Number. 23. The difference between two pressures is.
Option A. vacuum pressure.
Option B. differential pressure.
Option C. static pressure.
Correct Answer is. differential pressure.
Explanation. Differential pressure is the difference between two pressures (such as inside and outside the aircraft cabin).

Question Number. 24. What torque loading would you apply to a nut if the force is 50 lbs, exerted 2 feet from its axis?.
Option A. 100 lbs.ft.
Option B. 600 lbs.ft.
Option C. 251 lbs.ft.
Correct Answer is. 100 lbs.ft.
Explanation. Torque loading = force * distance.

Question Number. 25. In a jack with a ram only on one side and hydraulic fluid applied from both sides.
Option A. a condition of hydraulic lock exists and no movement will take place.
Option B. the ram will move opposite to the side where the ram is due to pressure acting on differential areas.
Option C. the ram will move to the side where the ram is, due to pressure acting on differential areas.
Correct Answer is. the ram will move opposite to the side where the ram is due to pressure acting on differential areas.
Explanation. The non-ram side has a greater area, so the ram will be pushed from that side to the ram side.

Question Number. 26. Using the same hydraulic pressure, the force applied by a hydraulic jack of 4 sq. inch piston area.
Option A. will be half that applied by a similar jack of 2 sq. inch piston area.
Option B. will be equal to that applied by a similar jack of 2 sq. inch piston area.
Option C. will be twice that applied by a similar jack of 2 sq. inch piston area.
Correct Answer is. will be equal to that applied by a similar jack of 2 sq. inch piston area.
Explanation. Force = pressure * area.

Question Number. 27. A pressure of 100 PSI acts on two jacks in a hydraulic system, having piston areas 2 sq in and 4 sq in.
Option A. the smaller jack will exert a force of 50 lb and the larger a force of 25 lb.
Option B. the smaller jack will exert a force of 200 lb and the larger a force of 400 lb.
Option C. the two jacks will exert the same force.
Correct Answer is. the smaller jack will exert a force of 200 lb and the larger a force of 400 lb.
Explanation. Force = pressure * area. 100 * 2 = 200 lbs. 100 * 4 = 400 lbs.

Question Number. 28. The purpose of an accumulator in a hydraulic system is to.
Option A. collect air from the hydraulic fluid, thus reducing the requirement for frequent bleeding.
Option B. relieve excess pressure.
Option C. store hydraulic fluid under pressure.
Correct Answer is. store hydraulic fluid under pressure.
Explanation. An accumulator stores hydraulic pressure for use when the main pressure pump fails.

Question Number. 29. If the hydraulic system accumulator has a low air pressure, it will cause.
Option A. rapid pressure fluctuations during operation of services.
Option B. rapid movement of the operating jacks.
Option C. slow build up of pressure in the system.
Correct Answer is. rapid pressure fluctuations during operation of services.
Explanation. The secondary purpose of an accumulator is to damp out pressure fluctuations.

Question Number. 30. The specific torque loading for a bolt is 50 lbs.ins but an extension of 2 inches is needed to reach the bolt in addition to the 8 inches torque wrench. What will the actual reading?.
Option A. 54 lb.ins.
Option B. 40 lb.ins.
Option C. 60 lb.ins.
Correct Answer is. 40 lb.ins.
Explanation. New torque reading = desired torque x L/(x+L). 50 * 8/10 = 40 lb.ins.

Question Number. 31. If 1500 psi hydraulic pressure is pumped into an accumulator, with a pre-charge air pressure of 1000 psi the gauge will read.
Option A. 2500 psi.
Option B. 1500 psi.
Option C. 1000 psi.
Correct Answer is. 1500 psi.
Explanation. The accumulator pressure gauge reads the hydraulic pressure only when it is above the charge pressure.

Question Number. 32. Young's modulus is.
Option A. stress * strain.
Option B. strain / stress.
Option C. stress / strain.
Correct Answer is. stress / strain.
Explanation. Young's Modulus (E) is the ratio Stress / Strain.

Question Number. 33. A cylinder filled with water to half a metre will exert a pressure of.
Option A. 4.9 Pa.
Option B. 4900 Pa.
Option C. 49 Pa.
Correct Answer is. 4900 Pa.
Explanation. Pressure = density * gravity * height = 1000 (for water) * 10 * 0.5 = 5000 Pa. Answer is 4900 Pa because gravity is slightly less than 10 (9.81 to be exact).

Question Number. 34. A mass of 10kg placed 2 metres away from a pivot will have a moment of.
Option A. 196 NM.
Option B. 50 NM.
Option C. 20 NM.
Correct Answer is. 196 NM.
Explanation. 10 kg = 10 * 9.8 = 98N. Moment = force * radius = 98 * 2 = 196 Nm.

Question Number. 35. 25 litres of fuel exerts a pressure of 10KPa. If a further 125 litres is added, the pressure will now be.
Option A. 50 kPa.
Option B. 60 kPa.
Option C. 40 kPa.
Correct Answer is. 60 kPa.
Explanation. Total Fuel = 150 litres = 6 * 25. 6 * original pressure = 60 kPa.

Question Number. 36. 1000 lb/in2 is in an accumulator. If 3000 lb/in2 of hydraulic fluid is pumped in, what is the pressure on the air side?.
Option A. 3000 lb/in2.
Option B. 4000 lb/in2.
Option C. 1000 lb/in2.
Correct Answer is. 3000 lb/in2.
Explanation. The piston does not move until the hydraulic pressure exceeds 1000 psi. From then on, the air and hydraulic pressures are equal (at all times that the piston is off its stops).

Question Number. 37. A fractional decrease in volume of a material when it is compressed is a function of the.
Option A. compressive strain.
Option B. compressive strain.
Option C. bulk modulus.
Correct Answer is. bulk modulus.
Explanation. Bulk modulus = ratio of change in pressure to the fractional volume compression.

Question Number. 38. A ram has a piston with 2 in2. Another ram with a piston of 4 in2 will provide.
Option A. the same force.
Option B. double the force.
Option C. square the force.
Correct Answer is. double the force.
Explanation. Double the area = double the force. (However, if the question said double the radius or diameter, the force is a square of that, i.e 4x).

Question Number. 39. How much force is exerted by piston if it is subjected to a pressure of 3000 Pa and has surface area of 2.5 m2?.
Option A. 7500 N.
Option B. 3000 N.
Option C. 1200 N.
Correct Answer is. 7500 N.
Explanation. Force = pressure * area = 3000 * 2.5 = 7.5 N.

Question Number. 40. A force of 10 million Newton’s is expressed numerically as.
Option A. 10 MN.
Option B. 10 MN.
Option C. 1 MN.
Correct Answer is. 10 MN.
Explanation. million Newtons = 10 MN (MegaNewtons).

Question Number. 41. A millilitre is equal to.
Option A. one million litres.
Option B. one millionth of a litre.
Option C. one thousandth of a litre.
Correct Answer is. one thousandth of a litre.
Explanation. A millilitre = 1/1000 litre.

Question Number. 42. If a square has an area of 9m2, one side is.
Option A. 3 m.
Option B. 3 m2.
Option C. 3 sq. m.
Correct Answer is. 3 m.
Explanation. 3 m * 3m = 9 m2.

Question Number. 43. A vector quantity is a quantity which.
Option A. possesses sense, magnitude and direction.
Option B. possesses direction only.
Option C. possesses sense only.
Correct Answer is. possesses sense, magnitude and direction.
Explanation. A vector quantity has magnitude AND direction. (sense and direction are the same thing).

Question Number. 44. One atmosphere is equal to.
Option A. 1.22 kg/m2.
Option B. 14.7 lbf/in2.
Option C. 28.9 inches of Hg.
Correct Answer is. 14.7 lbf/in2.
Explanation. atmosphere = 14.7 pounds-force (lbf) per square inch.

Question Number. 45. Strain is calculated by.
Option A. Original Length * Extension.
Option B. Extension ÷ Original Length.
Option C. Original Length ÷ Extension.
Correct Answer is. Extension ÷ Original Length.
Explanation. Strain = change in length divided by original length.

Question Number. 46. When a twisting force is applied to a bolt, what stress is exerted on to the head?.
Option A. Shear.
Option B. Compressive.
Option C. Torsion.
Correct Answer is. Torsion.
Explanation. A twisting force applied to a bolt produces 'torsion stress' (which technically is a form of shear). 

Question Number. 47. When you overstress a steel bar, what is the point called where it does not return to its original form?.
Option A. Plastic limit.
Option B. Elasticity limit.
Option C. Deformation limit.
Correct Answer is. Elasticity limit.
Explanation. The point at which the stressed bar does not return to its original form is called the 'elastic limit'. 

Question Number. 48. The formula for calculating shear is.
Option A. force ÷ cross-sectional area.
Option B. force * area.
Option C. force ÷ area parallel to the force.
Correct Answer is. force ÷ area parallel to the force.
Explanation. Formula for shear (stress) is Shear stress = force/area parallel to force.

Question Number. 49. A force 10 N is placed 2 Meters from a pivot point, what is the moment?.
Option A. 20 Nm.
Option B. 20 Nm.
Option C. 80 Nm.
Correct Answer is. 20 Nm.
Explanation. N at 2 m distance produces 10 * 2 = 20 Nm.

Question Number. 50. If a tensile load is placed on a bar, it will.
Option A. bend.
Option B. crush.
Option C. stretch.
Correct Answer is. stretch.
Explanation. tensile load placed on a bar will stretch it.