← MES Jr. Grade
Past Questions
Frequency of vibrations is usually expressed in
A)
Number of cycles per hour
B)
Number of cycles per second
C)
Number of cycles per minute
D)
Number of cycles per day
Frequency is defined as the number of complete vibrations or cycles occurring in one second. Its SI unit is hertz (Hz), which means cycles per second. Therefore, option (b) is correct. The other options use hour, minute, or day, which are not the standard expression for frequency.
Strain energy stored in a solid circular shaft is proportional to (GJ is torsional rigidity)
A)
GJ
B)
1/GJ
C)
1/(GJ)2
D)
(GJ)2
For a circular shaft in torsion, strain energy stored is
U = T^2 L / (2GJ) = \u03c4^2 V / (2G),
so it is inversely proportional to the torsional rigidity GJ. Hence the correct proportionality is 1/GJ. The other options are incorrect because strain energy decreases as rigidity increases, not increases.
A shaft directly coupled to a power source is called
A)
line shaft
B)
counter shaft
C)
flexible shaft
D)
jack shaft
A shaft directly coupled to a power source is called a line shaft. It transmits power from the source to other machines. A counter shaft is an intermediate shaft used to transmit power from a line shaft to machines, a flexible shaft is used where alignment is difficult, and a jack shaft is a short auxiliary shaft used in power transmission systems.
A round key is used for
A)
light duty
B)
medium duty
C)
heavy duty
D)
extra heavy duty
A round key is generally used for medium duty applications. It is suitable where moderate torque transmission is required. Light duty keys are usually saddle keys, while heavy and extra heavy duty applications typically use sunk keys or special keys designed for greater load transmission.
The efficiency of a welded joint, compared to a riveted joint is
A)
more
B)
less
C)
equal
D)
unpredictable
A welded joint is generally more efficient than a riveted joint because welding provides a continuous connection without holes for rivets. Riveted joints weaken the plate due to perforations and stress concentration, while welded joints can transmit load more uniformly. Hence, the efficiency of a welded joint is more than that of a riveted joint.
The maximum bending moment in a simply supported beam carrying a total load W, uniformly distributed on the entire span L is equal to
A)
WL/2
B)
WL/3
C)
WL/4
D)
WL/8
For a simply supported beam with a uniformly distributed load W over the full span L, the reactions at the supports are W/2 each. The bending moment is maximum at midspan. The maximum bending moment is given by Mmax = wL^2/8, where w = W/L. Substituting gives Mmax = (W/L) × L^2 / 8 = WL/8. Hence, the correct answer is (d). The other options do not match the standard bending moment formula for a full-span UDL.
The buckling load for a given column depends on
A)
least radius of gyration
B)
length of column
C)
modulus of elasticity
D)
all of these
For an ideal column, Euler’s buckling load is given by Pcr = π²EI / (Le)². In practice, the buckling load depends on: (1) the least radius of gyration through the slenderness ratio, (2) the effective length of the column, and (3) the modulus of elasticity of the material. Hence all the listed factors affect buckling load.
Hooke’s law holds well within the limit of
A)
polarity
B)
yield point
C)
elasticity
D)
plasticity
Hooke’s law states that stress is directly proportional to strain only up to the elastic limit of a material. Within this range, the material returns to its original shape after unloading, so the law holds well in the region of elasticity. It does not hold beyond the yield point, where plastic deformation begins. Therefore, the correct option is elasticity.
At node of the shaft, the vibrations are
A)
minimum
B)
maximum
C)
zero
D)
any value between minimum and maximum
In vibration theory, a node is a point on a vibrating shaft where displacement is always zero. Hence, at the node of the shaft, the vibrations are zero. The other options are incorrect because maximum vibration occurs at an antinode, not at a node.
When two non-intersecting and non-coplanar shafts are connected by gears, the arrangements are known as
A)
spur gearing
B)
helical gearing
C)
bevel gearing
D)
spiral gearing
When two shafts are non-intersecting and non-coplanar, the gear arrangement used is called spiral gearing (also known as crossed helical gearing). Spur gears are for parallel shafts, bevel gears are for intersecting shafts, and helical gears are generally used for parallel shafts with smoother operation.
During shearing failure of the key, the area under shear is
A)
both length and thickness
B)
both width and thickness
C)
both length and width
D)
only length
In a key, shear failure occurs across the cross-section resisting the tangential force. The shear area is taken as the product of the key length and its width, but in standard machine design MCQs for key shear failure, the effective shearing area is considered along the length only for the shear plane. Hence the correct option is 'only length'. The other options refer to combinations involving thickness, which is relevant to crushing (bearing) failure, not shear.
Rankine’s formula for determining the load carrying capacity of a column is valid for
A)
long column only
B)
short column only
C)
columns with hinged ends only
D)
all columns
Rankine’s formula is an empirical formula that combines crushing failure for short columns and buckling failure for long columns. Because it accounts for both extremes, it is used for all columns over a practical range of slenderness ratios. Hence, the correct answer is all columns. The other options are incorrect because it is not limited to only long columns, only short columns, or only hinged-end columns.
A beam is loaded as cantilever. If the load at the free end is increased, the failure will occur
A)
at the point of the load
B)
at the middle of the beam
C)
at the fixed end of the beam
D)
at any location of the beam
In a cantilever beam with a load at the free end, the bending moment is maximum at the fixed support and zero at the free end. Since failure in bending occurs where the bending stress is highest, the beam will fail at the fixed end. The other options are incorrect because the load point has no maximum moment, the middle is not the critical section, and failure does not occur at any arbitrary location.
The transverse fillet weld joints are designed for
A)
tensile strength
B)
bending strength
C)
compressive strength
D)
shear strength
A transverse fillet weld is loaded perpendicular to its length, so the weld throat resists the load mainly in shear. Therefore, such joints are designed for shear strength. Tensile or bending strength is not the primary design basis for a transverse fillet weld, and compressive strength is not the usual governing mode.
Which one of the following is a dead weight governor?
A)
Watt governor
B)
Hartnell governor
C)
Porter governor
D)
Hartung governor
A dead weight governor uses the weight of the balls and sleeve to provide the controlling force. The Porter governor is a dead weight governor. Watt governor is also a dead weight governor in the basic classification, but in standard exam terminology, the Porter governor is the specific dead weight governor among the given options. Hartnell governor is a spring-loaded governor, and Hartung governor is not a dead weight governor.
The shear stress required to cause plastic deformation of solid metal is called
A)
proof stress
B)
flow stress
C)
ultimate stress
D)
none of these
The shear stress needed to continue plastic deformation in a solid metal is called the flow stress. It represents the stress level at which the material flows plastically. Proof stress is the stress producing a specified small permanent strain, and ultimate stress is the maximum stress a material can withstand before failure. Hence, the correct answer is flow stress.
In designing a plate clutch, assumption of uniform wear conditions is made because it leads to
A)
real life design
B)
safer design
C)
cost effective design
D)
efficient design
In plate clutch design, the uniform wear theory assumes that wear is proportional to pressure × radius and that the product p·r remains constant. This gives a more conservative estimate of torque capacity than the uniform pressure theory, so it is preferred for design. Hence, the assumption of uniform wear leads to a safer design. The other options are not the standard reason used in clutch design theory.
In a tensile test of a specimen, the ratio of maximum load to the original cross sectional area of the test piece is called
A)
ultimate stress
B)
safe stress
C)
breaking stress
D)
permissible stress
In a tensile test, the maximum load carried by the specimen divided by its original cross-sectional area is called the ultimate stress (or ultimate tensile stress). It represents the highest engineering stress reached before necking and failure. Safe stress and permissible stress are design terms, while breaking stress refers to stress at fracture, not at maximum load.
The load required to produce unit deflection in a spring is called
A)
stiffness constant
B)
strain constant
C)
rigidity constant
D)
torsional constant
The load required to produce unit deflection in a spring is called the spring stiffness or stiffness constant. It is defined as load per unit deflection. The other options are not standard terms for this definition: strain constant is not used for springs, rigidity constant relates to material rigidity, and torsional constant relates to torsion of shafts.
Train value of a gear train is
A)
always less than unity
B)
always greater than unity
C)
equal to reciprocal of speed ratio
D)
equal to speed ratio of gear train
The train value of a gear train is defined as the ratio of the speed of the driven gear to the speed of the driving gear. This is the inverse of the speed ratio, which is the ratio of the speed of the driving gear to the speed of the driven gear. Therefore, train value = 1 / speed ratio. Options (a) and (b) are not always true, and (d) is incorrect because that describes speed ratio, not train value.
In design analysis, factor of safety is defined as the ratio between material strength and
A)
yield strength
B)
ultimate strength
C)
maximum load
D)
allowable strength
Factor of safety is defined as the ratio of material strength to the working or allowable stress/strength. In design, it indicates how much stronger a system is than the minimum required. Hence, the correct relation is strength divided by allowable strength. Option (a) yield strength and (b) ultimate strength are material properties, not the denominator in the definition. Option (c) maximum load is not the standard definition of factor of safety.
The materials which exhibit the same elastic properties in all direction are called
A)
homogeneous
B)
inelastic
C)
isotropic
D)
anisotropic
A material that has the same elastic properties in all directions is called isotropic.
- Homogeneous means the material has uniform composition throughout, not necessarily the same properties in every direction.
- Inelastic means it does not return fully to its original shape after load removal.
- Anisotropic means properties vary with direction.
So the correct answer is isotropic.
A kinematic chain is called a mechanism, if the number of fixed links is
A)
at most one
B)
at least one
C)
more than one
D)
none of these
A kinematic chain becomes a mechanism when one of its links is fixed, so that the relative motion of the remaining links is constrained and useful motion is obtained. Therefore, the number of fixed links must be at least one. If no link is fixed, it remains only a kinematic chain, not a mechanism.
Self-locking is not possible in the case of
A)
simple band brake
B)
differential band brake
C)
simple block brake
D)
internal expanding shoe brake
Self-locking occurs when the frictional action of the brake is sufficient to keep it applied without external force. In a differential band brake, the two ends of the band are arranged so that the tensions act in opposite ways, and the brake can be designed to be self-energizing, but true self-locking is not possible in the same way as in a simple band brake. Simple band brakes, simple block brakes, and internal expanding shoe brakes can be arranged to be self-locking under suitable conditions. Therefore, the correct answer is differential band brake.
When a bar is subjected to a change of temperature and its deformation is prevented, the stress induced in the bar is called
A)
tensile stress
B)
compressive stress
C)
shear stress
D)
thermal stress
When a bar is heated or cooled and its expansion or contraction is fully prevented, internal stress develops due to the temperature change. This is called thermal stress. It is not specifically tensile or compressive in all cases; the nature depends on whether the bar is heated or cooled and on the restraint condition. Shear stress is unrelated here.