Engineering mechanics one of the interesting subject of first year B.E. This subject has many practical applications and without this subject one cannot think about working of machines ,force systems and vehicles etc. One can say that this is the principal subject of mechanical engineering. Syllabus for the first year B.E.student is not very varst as this subject in itself is. But the whole syllabus cannot be discused through this medium. I have tried to help with the subject by discussing the experiments of E.M. as prescribed by the Nagpur University to help you solve the discussion questions to be written in the journal.The definations and diagrams will help to prepare this subject.

Q.1) Discuss the importance of load vercus efficiency graph?
Ans:-The graph shows the relationship load and efficiency. The efficiency can be easily found out for intermediate e values of load using graph. The curve starts from origin and being a stright line upto certain extent efficiency increases as load increases.
There after small increases in efficiency is observed when load increased.

Q.2) Discuss the importance of load vercus ideal effort graph?
Ans:-The graph gives relation between load and and ideal effort.As the graph is stright line effort increases with increases in load.

Q.1) Discuss the importance of load versus effort graph?
Ans:-Ideal effot is effort required to lift a load neglecting the machine friction. The graph shows relation between load and effort and it can be expressed as
P = mW + C.
m - slope of line
W - load
C - y intercept of line

Q.2) Discuss the causes of possible errors?
Ans:- a)Experimental error. b)Manual error. c)Error due to friction.

Q.3) Discuss the fritional loss in machine?
Ans:-For an ideal machine Pi=W/(V.R.). At W=0 the effort=C and will lift up the load, for an actual motion of machine a effort Pf is required to overcome the friction at load W and is given by P - Pi which is
Pf = mW + C - W/(V.R.)
If increses with load.

Q.4) How should the effort vary with the load for an ideal machine? How does the plat after due to friction?
Ans:-For an ideal machine erergy supplied equals to useful warkdone suppose load lifting by idealmachine is ' W '.The applied effort is ' P 'and velocityratio is ' V '.When load moves a unit distance then distance coverded by effort is equal to ' U ' .
Therefore,energy supplied is equal to ' PV '.
Useful work done is equal to ' w '.
w = P .V
Therefore , W / P = V =mA
Hence for ideal machine effort vary directly with load.

Q.5) Of the various lifting machines known to you how would you decide which are to choose for a particular situation?For example which lifting machine is best suited in your opinion for the following jobs.
a)Lifting a drum of water from a well.
Ans:-Pulley.

b)Lifting a heavy consigment from ship.
Ans:-Crain.

c)Lifting the body of a truck for changing wheels.
Ans:-Jack.

Q.1) What will be the value coefficient of static friction if (a)both materials are glass and (b)if both materials are wood ?
Ans:- If both the materials are glass the coefficient of friction will be less,and if both materials are wood then coefficient of friction is more.

Q.2) Define angle of repose?
Ans:-It is the max. inclination of the plane at which a body can remain in equillibrium over the plane entirely by the assistance of friction is called angle of repose.

Q.3) Suppose a block is placed on the indine and there is no pulley and string etc. Can' t we find the coefficient of static friction by creating condition of downward impending motion ? By increasing the inclination 0 ; by adding more weight on the block ? Can we ? How would it compare with our method ?
Ans:- We can find coefficient ob static friction by creading a downward impending motion .This can be done slowly increasing the angle of inclination till the body just starts to move.At this stage angle of inclition will be equal to angle of friction . This practically will not possible be possible because body will mov very fast and motion will take place with in fraction of second and observation can ' t be taken.

Q.4) The assumption made in analysis of observation and frictional pulley inextensibility of string .How correction of masses and angle measured .How far are the assumptions justified and what are possible sources of error ?
Ans:- The error may be due to stright friction present in pully .May be mass measurment may not be acurate .Error in measurment of angle friction as angke is cal culated by geometric method.

Q.1) Differentiate between sliding friction and coil friction?
Ans:- Sliding friction
a) It is a friction experemied by a body when it slides over other body.
b) It is a type of dynamic friction.
c) It is comparatively more.

Q.2) What is importance and use of coil friction ?
Ans:-We can determine the tension experiecned by body when friction exits.We can determine the friction force experienced, we can also find minimum force required to keep it in equillibrium.

Q.3) What is the importance angle of lap and its practical application ?
Ans:- Angle of lap is useful to determine tension on both sides of string/rope.Greater the angle of lap lesser the tension at free end of ropes.

Q.1 )What are the reasons for the deviation in therotical value and expt. value?
Ans:-
a)The wts. used in expt may vary from actual value.
b)The least count of dial spring is not sufficiently small to read actual reading.
c)Human error.
d)The lengths are not measured correctly.

Q.2) Can a load postion be determined to obtained given reaction?
Ans:-Yes when reactionon the beam is given then by taking moment of those reactions and unknow values of load about a point ,and taking summesion along x and y direction. Then solving the equation simultaneously.

Q.3) Sketch various types of beams.
Ans:-

 

 

 

Q.4) Why generaliy beam is supported by one hinge and one roller supports ?
Ans:- When external forces are attached or applied to a body which is hinged from both end then the body may bend or break due to deforming force devepol due to external force ,and if both the supports are roller supports then is not fixed and it can move in any direction .
Hence one support is hing and other is roller support.

Q.5) Sketch various beam sections.
Ans:-

 

 

 

 

Q.1) What will be the effect on the forces if the tie is attached in such a fashion that point C is lower than point B ?
Ans:-If point c is lower than point B then than tension in string will reduce greatly and due to that jib will be compressed to such an extent that the forces in jib gecreases and set up becomes unstable .

Q.2) What is jib crane ?
Ans:-Jib crane setup consists of compressive member (jib) and tension member which is connected by a load.
The jib crane operates a principal of coplanner concurrent force system.
Thus for a jib crane to be in eqillibrium ,total forces should be balanced.

Q.3) What are the reasons for the error ?
Ans:-
a)Friction in jib
b)Error in measurment of lengths
c)Variation in value of wts.
d)Human error.

Q.1) Define "mass moment of inertia"
Ans:- Mass moment of inertia :- The moment of inertia about a given axis of rotation for a rigid body is defined as sum of product of mass of each particle and square of perpendicular distance from the axis of rotation. Moment of inertia plays important role in circular motion as that of mass in linear motion . Hence physical significance of M.I. is same as of mass. Hence it is called mass moment of inertia.

Q.2) Differentiate between inertia and moment of inertia.
Ans:- a) Inertia is the tendency of bodyto maintain its state of rest or of uniform motion while moment of inertia is the mass equivalent in the rotational motion.
b) Inertia is the tendency of a body while moment of inertia is a property of body which it gains in rotational motion.
c)Inertia is applicable to translational motion where as moment of inertia is applicable to angular motion.

Q.3) Diffenentiate between fly-wheel and solid disk wheel.
Ans:- a) Moment of inertia of fly-wheel is 5/4 times that of uniform disk.
b) Mass is uniformly distributed in case of disk while it is concentrated at the circumference of fly-wheel.

Q.4) In the expt. of determination moment of inertia what is the importance of accuracy in measurment of time ?
Ans:- Time measured is used to calculate angular velocity and linear velocity. If time is measred is accurate then angular velocity can becalculated accurately. Following are the factors causes error in measurment of time
a) Human error in starting and stopping the clock.
b) Least count of clock may not be sufficiently small.

Q.5) Explain why a flywheel should have a large M.I.?
Ans:As contribution of mass is away from the axis of rotation so flywheel should be have a large M.I..

Q.6) Can you suggest some alternative method for determing moment of inertia of a body about a given axis?
Ans:It can be found by first calculating centriod of area then find M.I.about centridal axis and now with the help of parallel and perpendicular axis principle transfer M.I. to required axis.