Engineering Mechanics Top mcq
As stated by the Lami’s theorem, the three forces must be
Coplanar
Equal
Non-concurrent
90o to each other
ANSWER: – Coplanar
Solution:-
Lami’s theorem states that, if three coplanar forces acting at a point be in equilibrium, then each force is proportional to the sine of the angle between the other two.”
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The system of forces whose line of action meet at a common point and there is no net force or a resultant force due to their effect is called____________.
Coplanar Forces
Collinear Forces
Concurrent Forces
Independent Forces
ANSWER: – Concurrent Forces.
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Concurrent force system is the system when _________.
Lines of action of all forces pass through a point
Lines of action of all forces are parallel to each other
Lines of action of all forces lie along same line
Lines of action of all forces are not parallel to each other
ANSWER: – Lines of action of all forces pass through a point.
Solution:-
Concurrent force system is a type of system of forces in which line of action of all the forces meet at a point.
If line of action of forces lie along the same line known as collinear system of forces.
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a couple is formed when
Two unequal and unlike parallel force acting on a body
Two unequal and like parallel force acting on a body
A couple is formed if two equal and opposite parallel forces act on a body in a plane.
Two equal and like parallel force acting on a body
ANSWER: – A couple is formed if two equal and opposite parallel forces act on a body in a plane.
Solution:-
A couple is formed if two equal and opposite parallel forces act on a body in a plane.
Ex. Moment couple formed while steering the automobile, opening a bolt etc.
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Weight always acts towards
Vertically downward
Vertically upward
Towards center of earth
None of these
ANSWER: – Towards center of earth.
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Forces are called concurrent when their lines of action meet in
One point
Two points
Plane
Perpendicular planes
ANSWER: – one point.
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A body is said to be in dynamic equilibrium
When it is in uniform motion along a straight line
When it is in uniform motion along a circular path
When it is moving with changing acceleration
When it possess instantaneous velocity
ANSWER: – When it is in uniform motion along a straight line.
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Coulomb force is also known as
Frictional force
Electromagnetic force
Gravitational force
Nuclear force
ANSWER: – Electromagnetic force.
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Two non-collinear parallel equal forces acting in opposite direction
Balance each other
Constitute a moment
Constitute a couple
Constitute a moment of couple
ANSWER: – Constitute a couple.
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A force is completely defined when we specify
Magnitude
Direction
Point of application
All of the above
ANSWER: – All of the above.
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The forces, which meet at one point, but their lines of action do not lie in a plane, are called
Coplanar non-concurrent forces
Non-coplanar concurrent forces
Non-coplanar non-concurrent forces
None of the above
ANSWER: – Non-coplanar concurrent forces.
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The center of gravity is a point through which:
The whole weight of the body acts
The whole mass is assumed to be located
Both A and B
None of the above
ANSWER: – The whole weight of the body acts.
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The forces, which meet at one point, but their lines of action do not lie in a plane, are called
Coplanar non-concurrent forces
Non-coplanar concurrent forces
Non-coplanar non-concurrent forces
Intersecting forces
ANSWER: – Non-coplanar concurrent forces.
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According to Lami’s theorem
Three forces acting at a point will be in equilibrium.
Three forces acting at a point can be represented by a triangle, each side being proportional to force.
If three forces acting upon a particle are represented in magnitude and direction by the sides of a triangle, taken in order, they will be in equilibrium.
If three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two.
ANSWER: – If three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two.
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When a body falls freely under gravitational force, it possesses __________.
Maximum weight
Minimum weight
No weight
No effect on its weight
ANSWER: – no weight.
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Centre of gravity of a triangle lies at the point of concurrence of
The right bisectors of the angle of the triangle
The median of the triangle
The altitude from the vertices of the opposite side
None of these
ANSWER: – the median of the triangle
Solution:-
The point where the three medians of the triangle intersect. The ‘center of gravity’ of the triangle One of a triangle’s points of concurrency.
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The body will be in equilibrium if the two forces are
Collinear and equal
Collinear and opposite
Collinear, equal and opposite
None of these
ANSWER: – Collinear, equal and opposite.
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Idler pulley is used
For changing the direction of motion of the belt
For applying tension
For increasing velocity ratio
All of the above
ANSWER: – For changing the direction of motion of the belt.
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a couple is formed when
Two unequal and unlike parallel force acting on a body
Two unequal and like parallel force acting on a body
Two equal and unlike parallel force acting on a body
Two equal and like parallel force acting on a body
ANSWER: – Two equal and unlike parallel force acting on a body.
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The ‘Crowning’ of the flat pulley is generally done
To reduce the belt friction
To prevent the belt joint from damaging the belt surface
To prevent the belt from running off the pulley
In case of cross belt drive only
ANSWER: – To prevent the belt from running off the pulley.
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Time taken by bodies to regain original shape after compression due to impact is known as.
Time of deformation
Time of restitution
Time of collision
None of these
ANSWER: – Time of restitution.
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For perfectly elastic bodies, the value of coefficient of restitution is
1
0.5 to 1
0 to 0.5
0
ANSWER: – 1.
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The value of coefficient of restitution for perfectly elastic collision is
0
0.33
0.5
1
ANSWER: – 1.
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The value of coefficient of restitution for perfectly inelastic collision
0
0.33
0.5
1
ANSWER: – 0.
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During inelastic collision of two particles, which one of the following is conserved
Total K.E. only
Total linear momentum only
Both linear momentum and K.E.
None of these
ANSWER: – Total linear momentum only.
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The sum of kinetic and potential energy of a falling body __________.
Is constant at all points
Varies form point to point
Is maximum at starting and goes on increasing
Is maximum at starting and goes on decreasing
ANSWER: – is constant at all points.
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If two bodies, one light and other heavy, have equal kinetic energy, which on has a greater momentum?
The heavy body
The light body
Both have equal momentum
Unpredictable
ANSWER: – the heavy body.
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Limiting force of friction is the
Tangent of angle between normal reaction and the resultant of normal reaction and limiting friction.
Ratio of limiting friction and normal reaction.
The friction force acting when the body is just about to move.
The friction force acting when the body is in motion.
ANSWER: – The friction force acting when the body is just about to move.
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Two bodies are in contact, the force of friction will
Depends upon the area of their contact
Depends upon relative velocity
Depends upon the roughness of the surface.
All of them
ANSWER: – Depends upon the roughness of the surface.
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An object will continue to accelerate until
The resultant force begins to decrease
The resultant force is zero
The velocity changes direction
The resultant force on it is continuously increased
ANSWER: – The resultant force is zero.
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The maximum frictional force which comes into play when a body just begins to slide over the surface of another body is known as
___________.
Sliding friction
Rolling friction
Limiting friction
None of these
ANSWER: – limiting friction.
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The dynamic friction is the friction experienced by a when the body
Is in motion
Is at rest
Is moving with uniform acceleration
None of above
ANSWER: – is in motion.
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In a perfect truss, the numbers of members should be
Where J is the number of joints.
2J – 3
J-1
2J-1
3J-2
ANSWER: – 2J – 3.