Bihar Polytechnic question paper of Engg. Mechanics
Engg. Mechanics 2019 (Odd)
Group A
1. Choose the most suitable answer from the following options :
1). Branch of mechanics which relates to bodies in motion any reference to is called :
(a) Kinematics
(b) Kinetics
(c) Both (a) and (b)
(d) None of these
2). Which of the following is a vector quantity?
(a) Energy
(b) Mass
(c) Work
(d) Force
3). S.I. unit of mass is:
(a) Pound
(b) Kilogram
(c) Gram
(d) All of the above
4). Couple moment is a:
(a) Bound vector
(b) Free vector
(c) Both (a) and (b)
(d) None of these
5). A body which does not deform under a normal load is called.
(a) Rigid body
(b) Plastic body
(c) Both (a) and (b)
(d) None of these
6). The component of a force'P' at right angle to its direction will be:
(a) 0.5P
(b) 1.5P
(c) 0.6P
(d) Zero
7). The number of reaction components possible at hinged support for a general loading is:
(a) Three
(b) Two
(c) Four
(d) Five
8). A beam which is hinged at one end and roller at other end is known as:
(a) Cantilever
(b) Simply supported beam
(c) Fixed beam
(d) All of the above
9). Limiting friction is ........ than sliding friction.
(a) Greater
(b) Less
(c) Both (a) and (b)
(d) None of the above
10). The force of friction depends upon the ...... of the surfaces in contact.
(a) Nature
(b) Area
(c) Both (a) and (b)
(d) None of the above
11). Centroid of a semicircle of radius 'R' from its base is at a distance of .......
(a) 2R/3Ï€
(b) 2R/5Ï€
(c) 3R/4Ï€
(d) 4R/3Ï€
12). The centre of gravity of a hemisphere is at a distance of ...... from its base, measured along a vertical radius 'R'.
(a) 2R/3
(b) 2R/5
(c) 3R/7
(d) 3R/8
13). The centre of gravity of a triangle lies at the point of intersection of :
(a) Medians
(b) Diagonals
(c) Both (a) and (b)
(d) None of the above
14). Two parallel forces 75 N and 50 N act on a body and have a resultant of 25N. Then two forces are:
(a) Concurrent forces
(b) Like parallel forces
(c) Unlike parallel forces
(d) None of these
15). The coefficient of friction '¢' and the angle of friction 'A' are related as :
(a) ¢ = Sin A
(b) ¢ = Cos A
(c) ¢ = Tan A
(d) None of these
16). A machine is said to be reversible when its efficiency is:
(a) Less than 50%
(b) Greater than 50%
(c) Both (a) and (b)
(d) None of these
17). Velocity ratio of third system of pulley having three pulleys is:
(a) 4
(b) 5
(c) 6
(d) 7
18). A machine is said to be ideal if :
(a) Its efficiency in 100%
(b) Its friction is zero
(c) Both (a) and (b)
(d) None of these
19). A screw Jack is used for:
(a) Cutting an object
(b) Lift a heavy load
(c) Both (a) and (b)
(d) None of these
20). Support of a beam may be:
(a) Fixed
(b) Hinge
(c) Roller
(d) All of the above
Group B
ANSWER ALL FIVE QUESTIONS.
(4×5=20)
2). Define the following terms:
(a) Dynamics
(b) Mass
(c) Scalar quantity
(d) Force
OR
The resultant of two forces P1 and P2 is P. If P2 is doubled, the new resultant is perpendicular to P1. Show that P2 = P.
3). Discuss conditions of equilibrium of a rigid body in two dimension.
OR
Write four types of beams as per support conditions with necessary sketches.
4). Describe the properties of couple in short.
OR
Explain the following terms:
(a) Centroid
(b) Cone of friction
5). Define the following terms:
(a) Friction
(b) Angle of repose
(c) Coefficient of friction
(d) Angle of friction
OR
Write laws of static friction.
6. Explain the following terms:
(a) Efficiency of a machine
(b) Mechanical advantage
OR
Differentiate between simple machine and compound machine.
Group C
ANSWER ALL FIVE QUESTIONS.
(6×5= 30)
7. The angle between the two forces of magnitude 80 N and 50 N is 60°. The 80N force is horizontal. Determine the magnitude and direction of resultant, if the forces are pulls.
OR
State and Explain Varignon's theorem of moment.
8. Describe free body diagram with example.
OR
Determine support reactions at A and B for the beam loaded as shown in figure 0.1
9. A block of weight W1 = 100N rests on an inclined plane and another weight W2 is attached to the first weight through a string as shown in figure 02. If the coefficient of friction between the block and plane is 0.3, determine the maximum value of W2 so that equilibrium can exist.
Neglect the weight of string.
OR
Describe advantages and disadvantage of friction.
10. Find the centroid of the angle section shown in figure 03.
OR
Find the centroid of the section shown in figure 04.
11. An effort of 50 N is required by a machine to lift a load of 500N. The distance moved by the effort is 63 cm and corresponding load movement is 6 cm. Determine mechanical advantage, velocity ratio and efficiency of the machine.
OR
Explain the following terms:
(a) Friction in machine
(b) Self locking machine
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