zoeyzhou0828
14th Sep 2015, 13:53
Hi, all
I am preparing module 2 and bought a 'questions' on club66 pro without study note. Now I found some questions I can not figure out. Please help or we can discuss together. Thank you. (It is very very very long)
The question below in Mechanics-Kinetics chapter,
58. If a force of 10lbf produces an acceleration of 2.5ft/sec2, on what mass is it acting?
A.25 slug B. 4 lb C. 4 slugs
The answer is C.
However, in Mechanics-Dynamics chapter,
40. In the engineer’s version of FPS system, the amount of mass when acted upon by 1lbf, experiencing an acceleration of 1ft/s2 is
A. 32.17lb B. 1lb C. 1lbf
The answer is B.
According to the explanation of Question 58, F=ma, 10=m*2.5, m=4 slug (which I think it is also under FPS system), the answer of 40 should be m=1/1=1 slug=14.59kg=32lb, but the system showed me 1lb. Is there any different calculation ways between this two questions?
And in Mechanics-Dynamics chapter
10. If the speed of a gyro is increased, the force required to process the gyro is
A. decreased B. remains the same C. increased
I have checked my text book, the rate of procession depends on the
1. Strength and direction of the applied force – the greater the force, the greater the rate of procession.
2. Speed of rotor – the higher the speed the less the procession.
3. Moment of inertia of rotor – the higher the moment the less the procession.
Since the speed of the gyro is increased, that means the procession of gyro decreased, so the force should be decreased. The explanation system gave me was Rigidity increased with RPM. The definition of the rigidity is “inertia”, it is nothing to do with the procession force. Please correct me if I was wrong.
In the first Thermodynamics chapter,
26. In a heat pump,
A. the condenser always loses heat B. the evaporator gains heat during the heating cycle
C. the pump operates in both direction
The answer is C.
But in another Thermodynamics chapter
47. In a heat pump,
A. the condenser loses heat B. flow cross the condenser is always in one direction
C. the compressor gains heat
The answer is A. I am confused about these two questions answers, I can not see any differences.
Still in the Thermodynamics chapter
43. If heat transfer is through radiation,
A. Mass is transported from one plane to another
B. Heat energy is transferred to the medium
C. Heat energy is not transferred to the medium
68. The transfer of heat through radiation is achieved by
A. warming up the interventing medium
B. the application of radio active isotopes
C. not warming uo the interventing medium
The answers for these two questions are B and A. According to Wiki, conduction and convection are heat transfer processed that require the presence of the medium. Radiation heat transfer is characteristically different from the other two in that it does not require a medium and in fact it reaches maximum efficiency in a vacuum. Can you explain to me why the answers system gave me is B and A?
The one below in the Mechanics – Fluid Dynamics
50. When a fluid compressed, its density
A. decreases B. does not change C. increases
The answer is C
But there are some questions in Thermodynamics such as
44. If pressure on a liquid increased, whilst temperature is held constant, the volume will be
A. increase B. remain constant C. decrease
The answer is B.
The explanation of 44 is liquid incompressible, that means 50 should be does not change. How can I know when I can use “ liquid incompressible” rule?
The last one Optics (Light),
88. The range of core diameters for optical fibers are
A. 10-120 microns B. about 500 microns C. 50-100 microns
The answer is C. According to Wiki, single mode fiber core diameter is 2-10 microns. Please correct me if I was wrong.
I am preparing module 2 and bought a 'questions' on club66 pro without study note. Now I found some questions I can not figure out. Please help or we can discuss together. Thank you. (It is very very very long)
The question below in Mechanics-Kinetics chapter,
58. If a force of 10lbf produces an acceleration of 2.5ft/sec2, on what mass is it acting?
A.25 slug B. 4 lb C. 4 slugs
The answer is C.
However, in Mechanics-Dynamics chapter,
40. In the engineer’s version of FPS system, the amount of mass when acted upon by 1lbf, experiencing an acceleration of 1ft/s2 is
A. 32.17lb B. 1lb C. 1lbf
The answer is B.
According to the explanation of Question 58, F=ma, 10=m*2.5, m=4 slug (which I think it is also under FPS system), the answer of 40 should be m=1/1=1 slug=14.59kg=32lb, but the system showed me 1lb. Is there any different calculation ways between this two questions?
And in Mechanics-Dynamics chapter
10. If the speed of a gyro is increased, the force required to process the gyro is
A. decreased B. remains the same C. increased
I have checked my text book, the rate of procession depends on the
1. Strength and direction of the applied force – the greater the force, the greater the rate of procession.
2. Speed of rotor – the higher the speed the less the procession.
3. Moment of inertia of rotor – the higher the moment the less the procession.
Since the speed of the gyro is increased, that means the procession of gyro decreased, so the force should be decreased. The explanation system gave me was Rigidity increased with RPM. The definition of the rigidity is “inertia”, it is nothing to do with the procession force. Please correct me if I was wrong.
In the first Thermodynamics chapter,
26. In a heat pump,
A. the condenser always loses heat B. the evaporator gains heat during the heating cycle
C. the pump operates in both direction
The answer is C.
But in another Thermodynamics chapter
47. In a heat pump,
A. the condenser loses heat B. flow cross the condenser is always in one direction
C. the compressor gains heat
The answer is A. I am confused about these two questions answers, I can not see any differences.
Still in the Thermodynamics chapter
43. If heat transfer is through radiation,
A. Mass is transported from one plane to another
B. Heat energy is transferred to the medium
C. Heat energy is not transferred to the medium
68. The transfer of heat through radiation is achieved by
A. warming up the interventing medium
B. the application of radio active isotopes
C. not warming uo the interventing medium
The answers for these two questions are B and A. According to Wiki, conduction and convection are heat transfer processed that require the presence of the medium. Radiation heat transfer is characteristically different from the other two in that it does not require a medium and in fact it reaches maximum efficiency in a vacuum. Can you explain to me why the answers system gave me is B and A?
The one below in the Mechanics – Fluid Dynamics
50. When a fluid compressed, its density
A. decreases B. does not change C. increases
The answer is C
But there are some questions in Thermodynamics such as
44. If pressure on a liquid increased, whilst temperature is held constant, the volume will be
A. increase B. remain constant C. decrease
The answer is B.
The explanation of 44 is liquid incompressible, that means 50 should be does not change. How can I know when I can use “ liquid incompressible” rule?
The last one Optics (Light),
88. The range of core diameters for optical fibers are
A. 10-120 microns B. about 500 microns C. 50-100 microns
The answer is C. According to Wiki, single mode fiber core diameter is 2-10 microns. Please correct me if I was wrong.