RRB JE Stage II : Mechanical Engineering Quiz | 22nd August

Dear aspirants,

RRB JE Stage II exam is scheduled to be conducted from 28th August to 1st September 2019. The overall merit for the selection will be made on the basis of the marks scored in stage II, so candidates need to prepare thoroughly for the second stage. To help the aspirants, Adda247 has come up with a study plan in which we will provide you daily quizzes of all technical subjects. The below quiz will be helpful for the candidates who opted Mechanical as the exam group in RRB JE stage II.

Q1. A large metacentric height in a vessel
(a) improves stability and makes periodic time of oscillation longer
(b) impairs stability and makes periodic time of oscillation shorter
(c) has no effect on stability or the periodic time of oscillation
(d) improves stability and makes the periodic time of oscillation shorter

S1. Ans.(d)
Sol. T=2π=√(k2/(GM).g)
Increasing the metacentric height gives stability of a floating, but an increase in the metacentric
height reduced the time period of rolling of the body.

Q2. Consider the following statements:
Filling up a part of the empty hold of a ship with ballasts will
1.reduce the metacentric height
2. lower the position of the centre of gravity
3.elevate the position of centre of gravity
4.elevate the position of centre of buoyancy
Which of these statements are correct?
(a) 1, 3 and 4
(b) 1 and 2
(c) 3 and 4
(d) 2 and 4

S2. Ans.(d)
Sol. Metacentric height does not depend on the ballasts, lower the position of the centre of gravity and elevate the position of centre of buoyancy.

Q3. Stability of a freely falling object is assured if its centre of
(a) buoyancy lies below its centre of gravity
(b) gravity coincides with its centre of buoyancy
(c) gravity lies below its metacentre
(d) buoyancy lies below its metacentre

S3. Ans.(c)
Sol. Stability of a freely falling object when centre of gravity lies below its metacentre

Q4. Match List-I with List-Il regarding a body partly submerged in a liquid and select the
Correct answer using the codes given below the lists:
List-I
A.Centre of pressure
B.Centre of gravity
C.Centre of buoyancy
D.Metacentre
List-lI
1.Point of application of the weight of displaced
2.Point about which the body starts oscillating when tilted by a small angle
3.Point of application of hydrostatic pressure force
4. Point of application of the weight of the body
Codes:
   A B C D
a) 4 3 1 2
b) 4 3 2 1
c) 3 4 1 2
d) 2 4 2 1

S4. Ans.(c)
Sol. (a) Centre of pressure point of application of hydrostatic pressure force
(b) Centre of gravity: point of application of the weight of the body
(c) Centre of buoyancy : point of application of the weight of displace liquid
(d) Metacentre: point about which the body starts oscillating when tilted by a small angle.

Q5. lf a piece of metal having a specific gravity of 13.6 is placed in mercury of specific gravity 13.6, then the
(a) metal piece will sink to the bottom
(b) metal piece will simply float over the mercury with no immersion
(c) metal piece will be immersed in mercury by half
(d) whole of the metal piece will be immersed with its top surface just at mercury leve

S5. Ans.(d)
Sol. When piece of metal and liquid have same specific gravity then metal piece will be considered as the part of liquid.

Q6. A bucket of water hangs with a spring balance. If an iron piece is suspended into water from another support without touching the sides of the bucket, the spring balance will show
(a) an increased reading
(b) a decreased reading
(c) no change in reading
(d) increased or decreased reading depending on the depth of immersion

S6. Ans.(a)
Sol. Since the water of bucket will exert force of buoyancy equal to the volume displaced by the iron block. Hence equal and opposite force will be exerted by iron block on water hence the reading of the spring balance will increase

Q7. Assertion (A): If a boat, built with sheet metal on wooden frame, has an average density which is greater than that of water, then the boat can float in water with its hollow face upward but will sink once it overturns.
Reason (R): Buoyant force always acts in the upward direction.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

S7. Ans.(b)
Sol. Both A and R is true, but R does not give sufficient explanation for phenomenon at A. Location of metacentre and centre of buoyancy decide about floating of a body.

Q8. If a vessel containing liquid moves downward withconstant acceleration g, then
(a) the pressure throughout the liquid mass is atmospheric
(b) the pressure in the liquid mass is greater than the hydrostatic pressure
(c) there will be vacuum in the liquid
(d) the pressure throughout the liquid mass is greater than atmospheric

S8. Ans.(a)
Sol. A fluid at rest, pressure varies as
dp/dz= -ρg
When fluid moves downward than,
dp/dz=ρg+ρg=0
p1=p2=constant
i.e. pressure throughout the liquid mass is atmospheric

Q9. Match List-l (Stability) and List-ll (Conditions) and select the correct answer using the codes given below the lists:
List-I
A. Stable equilibrium of a floating body
B. Stable equilibrium of a submerged body
C. Unstable equilibrium of a floating body
D. Unstable equilibrium of a submerged body
List-II
1. Centre of buoyancy below the centre of gravity
2. Metacentre above the centre of gravity
Centre of buoyancy above the centre of gravity
4. Metacentre below the centre of gravity
Codes:
    A B C D
(a)4 3 2 1
(b)2 3 4 1
(c)4 1 2 3
(d)2 1 4 3

S9. Ans.(b)
Sol. (a) Stable equilibrium of floating body: Metacentre above the centre of gravity.
(b) Stable equilibrium of submerged body: Centre of buoyancy above the centre of gravity.
(c) Unstable equilibrium of a body floating: Metacentre below the centre of gravity.
(d) Unstable equilibrium of a submerged body:Centre of buoyancy below the centre of gravity

Q10. If B is the centre of buoyancy, G is the centre of gravity and Mis the metacentre of a floating body, the body will be in stable equilibrium if
(a) MG =0
(b) M is below G
(c) BG=0
(d) M is above G

S10. Ans.(d)
Sol. Stability of floating body
(i) If M is above G, or GM is positive or BM> BG body is in stable equilibrium.
(ii) If M is below G, or GM is -ve or BM<BG. The body is unstable equilibrium.
(iii) If M and G coincide, or GM = 0 or BM= BG. The body is in neutral equilibrium.

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