lab manual mechanics-ii

8/2/2019 Lab Manual Mechanics-II

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Engineering Mechanics-II

Lab Manual

Department of Mechanical Engineering

International Islamic University Islamabad

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Experiment No: 01

Layout of Engineering Mechanics-II Lab

Layout: The setting of apparatus in specific order is called layout.

Product Layout: Arrangement as per required product.

Process Layout: Layout as specified process.

1. Square and V-thread: An apparatus to compare the efficiencies of square andV-thread.

2. Fly Wheel: Fly wheel is device to control the motion or reduce fluctuation.Application in fuel control, aero plane fuel rod.

3. Linear and Angular Velocity: Apparatus convert linear velocity into angularvelocity and vice versa.

4. Screw Jack: Used to lift load. To find efficiency and mechanical advantage ofscrew jack.

5. Inclined Plane: An apparatus used to find mechanical advantage of inclinedplane at different angles. To compare mechanical advantage of different angles.

6. Derrick Crane: It is also called moveable crane. It is used to lift heavy loads.7. Western Differential Pulley: Device to lift heavy loads through differential

gears.8. Worm and Worm Wheel: Device used to convert translational motion into

transverse motion.

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Experiment No. 02

a. To determine Mechanical Advantage of Inclined Plane.b. To compare Actual and Ideal Mechanical Advantage.

Theory:

Mechanical Advantage: Assessment of effective forces on rigid bodies is called

mechanical advantage.

Inclined Plane: Archimedes 3 century B.C discovered six simple machines. Inclined

plane is one of them. A flat/smooth surface which has ends at different heights is called

inclined plane.

Apparatus:

Inclined plane, pulley, weights, protector, meter rod, scale pan and spring balance.

Procedure:

First of all found the weight of trolley or roller and the scale pan with the help of

spring balance. Than clean the surface of inclined plane and adjusted to angle of 30.

Then I connected the trolley and the scale by a thread, which pass over a pulley. Then I

placed the trolley in middle of inclined plane and scale pan hangs freely. Then I

adjusted the weight in the scale pan till on gently tapping the inclined plane. The trolley

just moved I noted the readings i.e. P and W. Then I calculated the mechanical and

ideal advantage by formula

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M.A= W/P, I.M.A=l/h

Precautions:

1. Same inclination of load should be avoided.2. Load holder should be at center of plane.

Calculations:

Length of inclined plane= l

Height of upper end= h1

Height of lower end= h2

Height= h = h1-h2

Real mechanical advantage= l/h

S/No W(N) P(N) Angel I.M.A A.M.A

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Experiment #03

1-To compare actual and ideal mechanical advantage of inclined plane.

2-To derive relationship between angle and mechanical advantage (actual and

ideal) at different angles.

Apparatus:

-inclined plane

-pulley

-weight

-protector

-meter rod

-scale pan

-spring balance

Theory

Inclined plane:

An inclined plane is a flat surface that higher at one end. It make of moving things

easier

Mechanical advantage:

M.A is the ratio of output distance and input distance.

i.e M.A=output/input

Difference between ideal and actual mechanical advantage

In ideal mechanical advantage friction is ignored while in actual mechanical advantagefriction is considered.

Mechanical advantage of inclined plane

The mechanical advantage of inclined plane is equal to the length of slope divided by

the height of the inclined plane.

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Procedure:

First of all I found the weight of roller and scale pan with the help of spring balance.

Then I clean the surface of inclined plane and adjusted to an angle of 11 degree. Then I

connected the trolley and scale pan by thread, which passes over pulley. Then I placed

the trolley in middle of inclined plane, and inclined plane hangs freely. I placed load and

effort and noted the reading when moving just started

Thus finding value of p and w putting in formulas a.m.a=w/p and i.m.a=l/h get these

required advantages. We see that I.M.A and A.M.A are inversely proportional to angle.

Precautions:

1-roller should be placed at middle of inclined plane

2-reading should be taken at that time when movement starts.

3-mishanding should be avoided

4-angle should be adjusted carefully

Comments:

It is noted that I.M.A and A.M.A are different because friction is ignored in actual

mechanical advantage.

Table

s/no angle W(n) P(n) l h A.M.A I.M.A

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Experiment #04

To determine the mechanical advantage of screw jack

Apparatus:

-screw jack

-weights

-hanger

-thread

Jack (device)

A jack is a mechanical device used to lift heavy loads or apply great forces.

Mechanical jack

A mechanical jack is a device which lifts heavy equipment. The most common form isa car jack, floor jack or garage jack which lifts vehicles so that maintenance can beperformed. Car jacks usually use mechanical advantage to allow a human to lift avehicle by manual force alone. More powerful jacks use hydraulic powerto providemore lift over greater distances. Mechanical jacks are usually rated for a maximum

lifting capacity (for example, 1.5 tons or 3 tons)

Hydraulic jack

A hydraulic jack uses a fluid, which is incompressible, that is forced into a cylinder by apump plunger. Oil is used since it is self lubricating and stable. When the plunger pullsback, it draws oil out of the reservoir through a suction check valve into the pumpchamber. When the plunger moves forward, it pushes the oil through a discharge checkvalve into the cylinder. The suction valve ball is within the chamber and opens witheach draw of the plunger. The discharge valve ball is outside the chamber and openswhen the oil is pushed into the cylinder. At this point the suction ball within the chamber

is forced shut and oil pressure builds in the cylinder.

Pneumatic jack

A pneumatic jack is a hydraulic jack that is actuated by compressed air - for example,air from a compressor - instead of human work. This eliminates the need for the user toactuate the hydraulic mechanism, saving effort and potentially increasing speed.

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http://en.wikipedia.org/wiki/Mechanical_advantagehttp://en.wikipedia.org/wiki/Hydraulic_machineryhttp://en.wikipedia.org/wiki/Tonhttp://en.wikipedia.org/wiki/Hydraulic_machineryhttp://en.wikipedia.org/wiki/Tonhttp://en.wikipedia.org/wiki/Mechanical_advantage


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Sometimes, such jacks are also able to be operated by the normal hydraulic actuationmethod, thereby retaining functionality, even if a source of compressed air is notavailable

Screw jack

It is the most important and 90% used jack because it has ability of self locking. It isused to lift houses from foundation. The screw is pushed upward until l desired height isreached.

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Procedure

1-wrap the string round the circumference 0f the flanged table and pass it over thepulley

2-attach hanger to free end of the string

3-the weight which is placed on the head of screw is called load (w) and the weightwhich is placed in the hanger is called effort(p)

4-note the initial readings of w and p

5-note reading when moment starts.

6-repeat process three times varying w and p

7-draw graph between w and M.A

8-Draw graph between p and M.A

TABLE

s/no W(N) P(N) M.A=W/P

PRECAUTIONS

1-String should not be flexible to avoid extension

2-wraping string should be such that it ends at lower part of flanged table Comments

It was very simple experiment and we enjoy it.

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Experiment No: 05

To compare efficiencies of square and V-thread

Apparatus:

Square and v-thread apparatus, weights, hangers, steel rule, string.

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Theory:

A thread is a grove or removal of surface in specific order and angel. The square

thread form is common thread form for lead screws. It gets its name from the square

cross section of the thread.

The v-thread gets its name from the v like cross section of the thread. This thread wad

invented by Soviet Climber. Square thread has less life than v thread because of the

fact that square thread have greater contact area, hence greater friction and hence

more worn and tear.

Efficiency:

% E= W/P.V *100

Where W is load or resistance force, p is the effort force an v is the velocity ratio.

Velocity ratio= Distance moved by effort/ Distance mobbed by load.

Procedure:

1. First work the screw on the square thread.2. For one complete turn of a table, the effort works through the circumference of

the table and the load rises through the pitch of the square thread. Measurethese and calculate the velocity ratio v.

3. Now find the effort p that is just sufficient to raise the load w applied to the screw.

Do this for w= 0, 5, 10, 15..4. For each reading calculate the % efficiency.5. Next work the screw on the v-thread and calculate the corresponding velocity

ratio v.6. Applying the same set of loads. Find the respective corresponding efforts and

calculate the efficiency for each reading.

S/N0 Load W Effort P Efficiency=w/pv*100

Square V-thread square v-thread

Precautions:

1. Determine pitch of the screw carefully.2. Take care that effort is applied in such a way that the load is just raised and not

lowered.3. Before performing experiment check that apparatus is ok by turning the table by

hand.Experiment No: 06

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a. To compare efficiencies and M.A of square and v-thread.b. To draw relationship between n and M.A with the help of graph.

Apparatus:

Square and v-thread apparatus, weights, hangers and strings.

Theory:

A thread is a grove or removal of surface in specific order and angel. The square

thread form is common thread form for lead screws. It gets its name from the square

cross section of the thread.

The v-thread gets its name from the v like cross section of the thread. This thread wad

invented by Soviet Climber. Square thread has less life than v thread because of the

fact that square thread have greater contact area, hence greater friction and hencemore worn and tear.

Efficiency:

% n= W/P.V *100

Where W is load or resistance force, p is the effort force an v is the velocity ratio.

Velocity ratio= Distance moved by effort/ Distance mobbed by load.

Mechanical Advantage is the number of times a machine multiplies the input force. M.A

for square and v-thread is calculated by formula M.A=w/p.

Procedure:

1. First work the screw on the square thread.2. For one complete turn of a table, the effort works through the circumference of

the table and the load rises through the pitch of the square thread. Measurethese and calculate the velocity ratio v.

3. Now find the effort p that is just sufficient to raise the load w applied to the screw.Do this for w= 0, 5, 10, 15..

4. For each reading calculate the % efficiency.

5. Also calculate mechanical advantage for each reading.6. Next move the screw on the v-thread and calculate the corresponding velocity

ratio v.7. Draw graphs between M.A and w, M.A and p and also M.A and n.

S/No Effort p Efficiency=w/pv*100 M.A=w/p

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Precautions:

1. Determine pitch of the screw carefully.2. Take care that effort is applied in such a way that the load is just raised and not

lowered.3. Before performing experiment check that apparatus is ok by turning the table by

hand.

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Experiment No: 07

To determine Moment of Inertia of fly wheel by free falling method.

Apparatus:

Fly wheel apparatus, thread, weight, stop watch.

Theory:

A fly wheel is rotating mechanical device that is used to store rotational energy.

The Andalusion agronomist Ibn Bassal in 1060 in his Kitabal-Filaha, describes the

flywheel effect employed in a water wheel machine.

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Application of fly wheel is: Reciprocating engines, friction motors, punching and riveting

machines, aircraft fuel system.

Moment of Inertia: also called mass moment of Inertia, rotational inertia, polar moment

of inertia or the angular mass is a measure of an object resistance to changes to its

rotation. It is the property of the material.

M.O.I = mr2

It is different for different shapes of bodies. E.g for ball it is 2/5mr2. However for fly

wheel M.O.I = mght2/8^2N(N+n) where

M= mass

N= no of revolutions due to mass m

n= no of turns of thread.

T= total time of revolutions.

H= height

Procedure:

1. Wound a thread aver the flywheel also count number of turns also attach ahanger on the end side of the thread.

2. Put some weight on the hanger.3. Now release the weight and on the same instant start the stop watch.

4. Count the number of revolutions until flywheel stops, when the fly wheel stops atthe same instant stop the stopwatch and note the time t.

5. Calculate the moment of inertia by the formula.Precautions:

1. Turns of the thread should not overlap each other and they should be tight.2. Marking the center of flywheel can help counting number of revolutions.3. Take care while starting or stopping the stop watch.

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Experiment No: 08

To verify the relationship between angular and linear velocity

Apparatus

An axle mounted in bearings

Three differential diameters around a light cord is wrapped and a free and

carries a small mass

The axle also carriers a hand wheel at one end which has stop pin so that

exact number of revolutions can be held

Procedure

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If necessary remove the stop pin and wind the masses up so that all are

ear the axle, the replace the stoppin.it is convenient to have all the

masses level to start.the masses can be adjusted by screwing on their

indvidual adjuster. Measure the height of masses above the floor.

Remove the stop pin and under allow the shaft number of times, say five.

Then replace the stop pin. Again measure the respective axle diameters

and note your data in a suitable table.

Results

Fill in the table below with your experimental data and compute the

remaining values

Axle diameter

Intial height h1

final height h2

S=h1-h2

S/d

30mm 50mm 70mm

W=2s/rat

As the axle is rigid w and t are the same for all three diameters during themotion. Hence we may write

S1/r1=s2/r2=s3/r3

Comments

This experiment was very good

It is easy to perform

Precaution

Value should be taken accurately

Height should be taken accurately

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Masses should be taken accurately

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Experiment No: 09

i. To find tension in jib and tie of derrick crane

ii. To compare experimental and graphical value:

Theory

Tension: process of stretching something tight.

Jib: The arm of a mechanical crane

Tie :

A beam or rod that joins parts and gives support.

Derrick crane: A machine for hoisting and moving heavy objects,

consisting of a movable boom equipped with cables and pulleys and

connected to the base of an upright stationary beam.

Procedure

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Setup the apparatus as describe above. Adjust collar as required and

ensure that the forked of the jib is screwed well into the sleeve to allow for

adjustment after loading. Selecting suitable dimensions for the jib, the

height of the collar and carefully note the dimensions a, back and d show

in the sketch below. The hanger should not be fitted at this stage

Note the initial readings of the tie and jib laces. Suspend a suitable load

from the hook. Adjust the length of the tie by altering the cord and adjust

the length of the jib by revolving the jib sleeves until the original dimension

of the configuration are re-established. Now note the final readings of jib

and tie laces. Repeat the experiment for different loads.

Change the shape of the configuration an

D repeats the above experiments.

Result

Tabulate the results as follows

Dimensions Applied load

p(N)

Jib force J Tie force T

a b c d initial

final net initial

final Net

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Experiment No: 10

To find the velocity ratio, mechanical advantage and load lost in friction and the

efficiency of worm and worm wheel.

Apparatus:

1. Worm

2. Worm wheel

3. Weight

Theory :

A worm drive is a gear arrangement in which a worm (which is a gear inthe form of a screw) meshes with a worm gear (which is similar in

appearance to a spur gear, and is also called a worm wheel). The

terminology is often confused by imprecise use of the term worm gear to

refer to the worm, the worm gear, or the worm drive as a unit.

Like other gear arrangements, a worm drive can reduce rotational

speed or allow higher torque to be transmitted. The image shows a

section of a gear box with a worm gear being driven by a worm. A worm is

an example of a screw, one of the six simple machines.

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Procedure:

1. For one complete turn of pulley a wheel effort p is applied the worm moves the

worm wheel through teeth and for one complete turn of worm wheel the load wraises through a height equal to circumference of pulley hence velocity ratio.

2. V=dist moved by effort/dist moved by load.

3. Now find p which is just to raise the load w attached to worm wheel.

4. Do it for w=0, 4, 6, 8., mechanical advantage is given as

5. M .A=w/p, Efficiency=w/pv*100.

6. Calculate these for each reading. If the machine were ideal, the load L lifted by it

would satisfy the relation.

7. P* dist moved by effort=L*dist moved by load is L=pv.

8. Hence L-w or pv-w is called load lost due to friction.

s/no Load w(lds)

Effort p M.A=w/p % Efficiency=w/pv*100

Load lost lfriction=pv-w

Precautions:

1. Take care that effort is applied is such a way that loads are raised not allowed.

2. That value of effort p is to be considered just enough to raise the loads.

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Experiment: 11

To find the velocity ratio, mechanical advantage and the load lost in friction and

the efficiencies of a western differential pulley.

Apparatus:

1. Western differential pulley

2. Lock

3. Weights

Theory :

A differential pulley, sometimes called a "chain hoist," or sometimes

colloquially called a "chain fall," is used to manually lift very heavy objects

like car engines. It is operated by pulling upon the slack section of a

continuous chain that wraps around pulleys. The relative sizes of two top

pulleys determine the maximum weight that can be lifted by hand.

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Procedure:

1. For one complete turn off pulley at where effort p is applied, the worm moves the

worm wheel through teeth and for one complete turn of worm wheel the load wraises through a height equal to circumference of pulley.

2. Hence velocity ratio: V=dist moved by effort/dist moved by load.

3. Now find p which is just to raise the load w attached to worm wheel.

4. Do it for w=0, 4, 6, 8

5. Mechanical advantage is given as M.A=w/p. Efficiency=w/pv*100.

6. Calculate these for each reading. If the machine were ideal, the load l lifted by it

would satisfy the relation.

7. P*dist moved by effort=L*dist moved load is L=pv

8. Hence L-w or pv-w is called load lost due to friction.

9. Take w along x-axis and all other quantities along y-axis.

10.Velocity ratio=v=8x/1/2x=16

S.NO Load w(lbs)

Effort p(lbs)

Mechanicaladvantage=w/p

Efficiency=w/pv*100

Load lost infriction=pv-w

Precautions:

1. Take care that effort is applied in such a way that load is raised not Lowered.

2. That value of effort p is to be considered just enough to raise the loads.

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lab manual mechanics-ii

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