chandan ms lab assignment
TRANSCRIPT
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Contents
EXPERIMENT NO. 1.......................................................................................................................... 2
CENTRE OF GRAVITY............................................................................................................ 2
Conclusion:................................................................................................................................. 3
EXPERIMENT NO. 2..................................................................................................................... 4
COEFFICIENT OF STATIC FRICTION................................................................................... 4
Result:-........................................................................................................................................ 6
EXPERIMENT NO. 3..................................................................................................................... 7
TRIANGLE OF FORCE EXPERIMENT.................................................................................. 7
Result:......................................................................................................................................... 9
EXPERIMENT NO. 4................................................................................................................... 10
BELL CRANK LEVER EXPERIMENT.................................................................................. 10
Result:....................................................................................................................................... 12
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EXPERIMENT NO. 1
CENTRE OF GRAVITY
AIM: To locate the center of gravity for given objects, having uniform distribution of
mass.
Apparatus required:
Centre of gravity apparatus. Different types of uniform shapes.
Figure of centre of gravity apparatus
Theory:Centre of gravity of a body can be defined as the point through which resultants
of the gravitational force acting on the body acts or is concentrated for any orientation of
the body.
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Procedure:
Hang the object from any point and drop a weighted string from the samepoint.
Draw a line on the object along the string. Repeat the procedure for different points on the object. Now you have the lines drawn on the object which intersect at a particular point.
The centre of gravity is the point where the lines intersect. Repeat the steps 2 to 6 for given different objects having different shapes. Tabulate the results in a table.
Observation:
Shape Name Distance x, from geometric Centre Distance y, from geometric
Centre
Trapezoid 10 8.5
Circle 0 0Semi-circle 11 5.5
Triangle 8 6
Precaution:
Make sure that the strings of the apparatus are free from tension and are freelyhanged.
The weight or pointer hanged on to the string should be free from any tension
Make sure that the shapes are also hung freely and the string is properly fallingupon them.
`
Conclusion: Since from the above experiment we come to know about the most
significant property of the centre of gravity, and conclude that the total mass of the body
is concentrated on it.
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EXPERIMENT NO. 2
COEFFICIENT OF STATIC FRICTION
AIM:To determine the coefficient of friction under sliding condition between polished
glass surface and wooden block.
Apparatus Required:
Inclined plane apparatus. Different weight blocks Lubricating oil.
Figure of Inclined plane apparatus
Labelling:
Inclined track Load Hanger Inclined angle indicator Set of Carrier Set of weights
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Theory: Friction is defined as the imaginary force which opposes the cause of motion
that is it opposes the motion of a body when it moves or tends to move due to the action
of an external force on the body. While kinetic friction can be defined as the frictional
force that develops between mating surfaces when subjected to external force but there isno relative motion between them.
Procedure:
Level the inclined plane set in a horizontal position. Next, choose specimen and record its weight R. Then place the specimen onto the horizontal plane, in the mid span. Connect a cord to the specimen hook as provided. Run the cord over the pulley and place a hanger (0.1N) on to the other end of the
cord.
Put sufficient weights on to the hanger till it balances the specimen weightwithout sliding down the plane.
Repeat step 2 until step 6 for different specimens. Take note of the weight + hanger.
Observation:
Serial number F (gm) R (gm) 1 40 171.5 0.233
2 35 141.5 0.247
3 35 131.5 0.266
Formula used for calculating the static coefficient of friction is:
= f / RN
Calculation:
Average -:
(0.233+0.247+0.266)/3 = 0.746/3 = 0.248
Precaution:
The string or thread of the apparatus should be free from any tension.
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The pulley should be well lubricated. The weights should be added step by step and it should be ensured that the block
should not slide and the readings should be taken just before it slides.
Result:-Hence from the above experiment we can determine the coefficient of static
friction between two surfaces ( i.e between a polished glass surface and wooden block).
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EXPERIMENT NO. 3
TRIANGLE OF FORCE EXPERIMENT
AIM: To determine the experimental resolution of three static coplanar forces. To
show that if the forces are in equilibrium the triangle is closed and to show that if two
forces are known in magnitude and direction, the third must be the resultant of the
triangle of forces.
Apparatus Required:
Triangle of force apparatus. Different weight blocks.
Figure of Triangle of force apparatus-
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Theory: For equilibrium in a triangular force, the system will be at equilibrium only
when if the sum of forces acting at an equilibrium, then the algebraic sum of their
resolved part in any two perpendicular direction s are separated zero.
If three-force body is subjected to only three forces. For the equilibrium, the actingforces must be concurrent and must from a closed triangle.
F1
Law of sines can then be used to solution of force
SinA/A=sinB/B=sinC/C F2
Where in=sinB=sinC=angle between 2 forces F3
Procedure:
Place the apparatus on a level table. Sketch the desirable free body diagram. Loosen the turning knob of the pulley bracket (E). Mount the three pulley bracket
on the protractor plate.
Set the pulley bracket to desirable angle. Tighten the turning knob.
Adjust both of the screws at the side of the bracket. Do not over tighten norloosen the screws. Make sure the pulley can turn smoothly.
Place the ring (A) to the centre of the protractor. Place the three cords to the three pulleys. Place a weight hanger (B) to each of the cord. Place the desirable weights to each of the hanger and observe the movement of
the ring.
If the ring touches the centre rod, this implies that the system is not inequilibrium position.
Repeat the experiment with different angles and different weights applied.
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Observation:
1 2 3
F1 1() F2 2() F3 3()
Case 1 0.45 0 0.5 122 0.45 257
Case 2 0.45 0 0.4 97 0.55 224
Case 3 0.45 0 0.45 105 0.55 240
Calculations
fx = 4410* sin0+3920*sin230+3920*sin110
= 4410*1+3920*sin230+3920*sin110
= 4410+3920*(-0.76) +3920(0.93)
= 5076.4
fy =4410*cos0+3920*cos230+ 3920*cos110
= 4410*1+3920*sin230+3920*(-0.34)
=4410+3920*(-0.64)+3920*(-0.34)
= 568.4
Precaution:
The string or thread of the apparatus should be free from any tension. The pulley should be well lubricate The weights should be added step by step. Resolution of force is to be maintained.
Result:The resolution of three static coplanar forces is determined and the forces are in
equilibrium in the triangle is proved.
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EXPERIMENT NO. 4
BELL CRANK LEVER EXPERIMENT
Aim:To verify the principle of moment using Bell Crank Lever.
Apparatus Required:
Bell Crank Lever apparatus. Different weight blocks Hanger
Figure of Bell Crank Lever apparatus -
Theory:Moment of force about a point is defined as the turning tendency of a force
about that point. It is measured by the product of force and the perpendicular distance of
line of action of force from that point.
Mathematically M= FxL
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Where F= force acting on the body
L= perpendicular distance between the referenced point and the line of action of
force.
Procedure:
Make the longer arm of the lever horizontal by adjusting with wing nut providedat the end of spring balance longer screw, by using a level when there is no load
on longer arm.
Note the initial spring balance reading. Place the stirrup on any one groove of the arm and hang a small weight (W) on
the hook. This will make the longer arm move down ward and the spring balance
will show some reading on balance.
Note the final spring balance reading. Change the position of load and repeat the steps 3 to 4 for different loads and
calculate the moments.
Tabulate the results in a table.
Sr. No. Load(F)Final Spring
reading(W)
Distance ofload from
hinge point(x)
y
1 100+73.5 10013 22.55
2 100+73.5 20023 22.55
3 100+73.5 30033 22.55
4 100+73.5 400
43 22.55
Formula
Use the formulae below to calculate the moments on bell crank lever:
M1= Spring Force (F)x
M2= Weight (W)y
M1 M2
2255.5 2255.5
3990.5 3990.5
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5725.5 5725.5
7460.5 7460.5
For example:
Calculations:
Here, M1= F*x;
M2 = W*y;
M1= 173.5*13=2255.5
M2 = 100*22.55=2255.5
M1=M2
(Hence proved)
Precaution
Check for zero error. Add the weight gradually There should be minimal disturbance as long as the pointer is concerned Only one person must take all the readings, because eye judgement will vary from
individual to individual
Weight should not touch the table The pointer should exactly coincide with the mark on the bell crank lever. The optimum starching of spring should be kept in mind The apparatus should be kept on smooth and level surface. Proper lubrication of the joints of two arms of the lever so as to reduce frictional
force.
Result:
From the value obtained above, its clear that the observed and calculated values
obtained for the value of spring forces are nearly equal and within the permissible
experimental error limit.
Hence, the law of moment stating that the moment of a force about an axis is
equal to the sum of moment of its components about the same axis has been verified.