RRB JE Stage II : Mechanical Engineering Quiz | 24th 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. The submerged body will be in stable equilibrium if the centre of buoyancy B
(a) Is below the centre of gravity G
(b) Coincides with G
(c) Is above the meta-centre M
(d) is above G

S 1. Ans.(d)
Sol. Submerged body will be in stable equilibrium if the centre of Buoyancy (B) is above the centre of gravity (G). For neutral equilibrium: Centre of buoyancy is equal to centre of gravity For unstable equilibrium Centre of buoyancy is less than centre of gravity.

Q2. The stability of a floating body is obtained when its
(a) Centre of gravity is below the centre of buoyancy
(b) Metacentric height is negative
(c) Metacentric height is positive
(d) Metacentric height is zero

S2. Ans.(c)
Sol. Stability of floating body is obtained when its metacentric height is positive i.e. GM is positive
GM=(I/V)-BG

Q3. Assertion (A) : Increasing

the metacentric heigh gives greater stability, but reduces the period o roll so that the vessel is less comfortable for passengers
Reason (R): Warships and racing yachts heave larger metacentric height as their stability is more
important than comfort.
(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

S3. Ans.(b)
Sol. Relation between time period of oscillation () and metacentric height (GM) iS
T=2π(√k2/g(GM))
where g= acceleration due to gravity
K= radius of gyration

Q4. For stability of a floating body
(M metacentre, G = centre of gravity and B =centre of buoyancy)
(a) M should coincide with B and G
(b) M should lie below B and G
(c) M should lie above B and G
(d) M should lie between B and G

S4. Ans.(c)
Sol. For stability of a body, it should have positive metacentric height i.e M should lie above Band G

Q5. The resultant of all normal pressures on a body immersed in liquid acts
(a) through the centre of gravity of the body
(b) through the centre of pressure
(c) vertically upwards
(d) at metacentre

S5. Ans.(c)
Sol. The resultant of all normal pressures always acts vertically upwards

Q6. A bucket of water is hanging from a spring balance. An iron piece iS suspended into water without touching any of the side of bucket from another support The spring balance reading will
(a) increase
(b) decrease
(c) remain the same
(d) depend on the depth of immersion

S6. Ans.(a)
Sol. As the iron piece is immersed in water it will experience an upward buoyancy force by the water of bucket. The water of bucket will experience an equal force downward and hence the spring balance reading will increase

Q7. A piece of wood of volume Vand specific gravity 087 floats on the surlace of a liquid of specific gravity 1.31 The portion of the body which is submerged in the liquid will be
(a) 0.335V
(b) 0.665V
(c) 0.87V
(d)0.13V

S7. Ans.(b)
Sol. Weight of piece of wood = Force of buoyancy
Vx 0.87 x 1000 = V x 1.31 x 1000
V’=0.665V

Q8. During floods, water entered an office having wooden tables. The position of tables, if floating will be
(a) legs downwards
(b) legs on sides
(c) legs upward
(d) Any position

S8. Ans.(c)
Sol. Since there is more mass towards the top of th table For stable equilibrium metacentric height should be +ve

Q9. What is the specific gravity of a marble stone which weighs 400 N in air, and 200 N in water? (g=10 m/s)
(a) 8
(b)6
(c) 4
(d)2

S9. Ans.(d)
Sol. specific gravity = weight in air/weight in air-weight in water =
(400/400)-200
=2

Q10. Consider the following statements:
1. If a small upward displacement is given to a floating body, it results in the reduction of the buoyant force acting on the body
2. A slight horizontal displacement does not change either the magnitude or the location of the buoyant force
Which of the above statements is/are correct?
(a) Both 1 and 2
(b) 1 only
(c) 2 only
(d) Neither 1 nor 2

S10. Ans.(a)
Sol. 1. Buoyant force is given by volume of displaced liquid. So, small upward movement will reduce
the volume of floating body is liquid and reduced displaced liquid. So Buoyant force decreases
2. The horizontal displacement will result in motion but not change in volume so no change in direction and magnitudes

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