twad mechanical engineering

8/19/2019 TWAD Mechanical Engineering

1/13

SE TION

A

1.

This question consists

of

TWENTY-FIVE sub-questions 1.1 -

1.25) of

ONE mark

each. For each of these sub-questions, four possible alternatives A, B, C and D)

are

given,

out

of which 0 N LY 0

NE

is correct. Indicate the

correct

answer

by

darkening the app rap riate bubble against the question number on the I

eft hand

side of the Objective Response Sheet ORS). You may use the answer ok

provided for any rough work,

i

needed.

1.1 The divergence of

vector

=

xl

+

y

+

z

is

1.2

1.3

1.4

b)

3

c) 0

Consider the system

of

equations given below:

x y =2

2X+2y=5

This system has

G

'

a) one solution b) o

sol

tion

c)

infinite solutions ut1ons

-1

c)

0

d)

Does

not

exist

The Gauss divergence t e s

certain

a) : · tegrals

b) surface

in

Is t Integrals

c)

vector

qu ti · o

ther

vector

quantities

d) line integra lume integrals

•

.5

For a s aded roller-follower driven with a disc cam,

return for

ase f transm1ttmg m ot1on

pressure angIe should be smaller during rise

than that dun

ng return for

ease

of transmitting motion

c) the pressure angle should be large dunng nse as well as dunng return for

ease

of

transm1ttmg m ot1on

d) the pressure angle does not affect the ease of transm 1t n g m ot on

1.6 The shape of the bending moment diagram for a uniform canti Iever beam

carrying a uniform I y distribu ted I oad over its I eng th is

a) a

straight

line b) a hyperbola


2/13

1. 7 In the

figure

shown, the spring deflects

by o

to position A the equilibrium

position when a mass m

is

kept on it.

During

free vibration, the mass

is

at

position B

at

same instant. The

change

in paten ti al

energy

of the

spring-mass

system from position A to position B is

l.B

1.9

a)

kx

2

m

B

p

bar

AB

is subjected to bending

but

bar B C is not subjected to bending

bar AB

is

not subjected to bending

but

bar BC is subjected

to

bending

neither bar

AB

nor

bar

B C is subjected to bending

both bars

AB

and BC

are

subjected to bending

1.10 The area moment of inertia of a square of size 1

unit

about its diagonal

is

1

a)

3

b) . .

4

1

c)

12


3/13

1.11 Which of the foil

owing

statement

is

correct?

1.12

1.13

1.14

1.15

(a)

Flywheel reduces speed fl uctu ati ons during a cycle for a constant Ioad,

but

flywheel does

not

control the mean speed of the engine

i

the

I

oad changes.

(b) Flywheel does not reduce speed

fluctuation during

a cycle

for

a constant

load, but

flywheel

does not control

the

mean speed

of the engine

i the load

changes.

c) Ga vernor controls speed fl uctuat ons dunng a cycle for a constant I b

govern

or

does

not

control

the mean

speed

of

the en gme 1

the

I

oad an .

(d)

Ga vernor controls speed flu ctuat1 ons dunng a cyd e for a

a d

govern

or

also

control

the mean speed

of the

engm e 1 the load o s.

The 5 Unit of kinematiC VISCOSity (v)

IS

~

(a)

m

/sec

(b)

kg/(m-sec) (c) m/sec

m ec

A static

flu d

can have

c;0

(a) non -zero normal

and

shear stress

(b) negat1ve normal stress

and

zero shearq

(c) pos

t1

ve n arm al stress and zero sh

Z r

s

(d)

zero normal stress

and

n o n z e r o s

A gas

having

a

negative

Joule-

on

oefficient

<

0),

when

throttled,

will

(a)

become cooler

(b)

become warmer

(c)

remain

at

the

s m e

e

(d)

either be cooler or

p e n d i n g

on the type of gas

Lumped nalysis of a solid

object suddenly

exposed to a

fluid

medium

at

a d n temperature

is

valid when

(a)

Biot

mber

.1

(b)

Biot

number>

0.1

a)

0.17

b) 0.21

c)

0.79

un1ter

<

0.1

(d)

Fourier

number>

0.1

react1 on

tu

rb 1n e

A

T

L=D

---- ~

I - A l


4/13

1.18 In descending order of

magnitude, the thermal

cond ucti vi

ty

of

a)

pure

iron, b)

I quid

water,

c) saturated water vapour

and

d) aluminum can be arranged as

a)

a b c d

b)

b c a d c) d a b c

d)

d c b a

1.19.

1.20. The cutting force in punching and blanking operations

mainly

epe

a) the

modulus

ofelastidty

of

metal b) the

shear s t r •

c) the bulk

modulus

ofmetal

1.21.

In ECM them

atenal

rem oval 1s due

to

d) the y

n

th

ofmeta

l c e m e n t

1.22.

1.23.

a) corrosion

c) fusion

Two pi ates of

the

same meta havi

electric

arc When

the

pI ate thick n

a)

adjusting

the

current

c)

d)

:nl sss are

to

be butt welded With

s welding

IS

achieved by

b)

adjusting the

duration

of

current

d) chang ng the electrode coatm g

assign

more

weight to

the

recent demand data

c) i ncl ud e new demand data in the average with

out

discarding the earlier data

d)

i ncl ud e new demand

data

in the average

after

discarding same

of

the

earlier

demand data


5/13

2. This question consists of TWENTY-FIVE sub-questions 2 .1 2.25) of

TWO

marks

each. For each of these sub-questions, four possible alternatives (A, B, C and D)

are given, out of which 0 N LY 0 NE is correct. Indicate the correct answer

by

darkening the app rap riate bubble

against

the question number on the

I

eft hand

side of the Objective Response Sheet (ORS). You may use the answer book

provided for any rough work,

i

needed.

2.1

The

minimum point of

the function

x) = x

3

/3 -

xis

at

a)

x = 1

b)

X = -1 c) x = 0

2.2. The rank

of

a 3 x 3 matrix C (

=

AB ), found

by

multiplying

< :J-zer

matrix A

of

size 3 x

1

and a non-zero row matrix B

of

size

1

x , 1

a)

0 b) 1 c) 2

d)

2.3.

An

unb1 a sed c01n 1 tossed three t1 m es. The prob abll0 ~ head turns up 1n

1 1 3

exactly two

cases 1s

J

a)

9 b) 8 A. - d) 8

2.4.

Two helical tensile

spnngs

of the sam · m ~ U also hav1ng 1dent1cal mean

sti

fm

ess

is

a) 1 c) 64 d) 128

'·'·

''

,.,. ~ ~ ' ~ ' ~ ' '

'' ''

0

..._\ +

~ -

b) 2cr

c)

3cr d) l.Scr

2.6.

~ ~ ~ gear 1n the figure 1s dnven clockwise at

100

rpm. The

ring

gear is held

~ a r y For the number of teeth shown on the gears, the arm rotates at

~ .

1ng80T

I J\ ,...,... ,......,. • • • • • • •


6/13

2 7. For the loading on truss shown in the figure, the force in member D is

E

lkN

lkN

a)

kN

b)

1 kN c) ./2kN

2.8. Bodies 1 and 2 shown in

the

figure

have

equal mass m. All s

The value of force P required to prevent sliding of body 2 on b

a) P=

2mg = 2./2

mg

•

d) P =

mg

2.9.

om

posed

of

two

mass ess rods

of

I

ength

I

he natural frequency of this assembly for

b)

the

linear

mom

en

tum

in

x and y directions are

conserved

but

the energy is not con served


7/13

(b)

the linear momentum in x and y directions

are

conserved and the energy is

also con served

(c) the

I

near

momentum

in x direction is conserved and the energy is also

conserved

(d)

the I

near

momentum in y direction is conserved and the

energy

is also

conserved

2.11. A

cyd

c heat engine does 50 kJ

of

work

per

cycle

f

the efficiency

engine is 75 , the heat rejected per cycle is

a)

1 6 ~ c J b) 3 3 ~ c J c) 3 7 ~ c J

3 3 2

2.12.

2.13.

h

Gate width


8/13

2.16.

For

air

at a given

temperature,

as the

relative

humidity

is

increased isotherm ally,

a) the wet bulb temperature and specific

enthalpy

increase

b) the wet bulb temperature and specific enthalpy decrease

c) the wet bulb

temperature

increases and specific

enthalpy

decrease s

d) the wet bulb temperature decreases and speci fie

enthalpy

in creases

2.17.

Water Prandtl

number=

6)

flows over a flat

plate

which is

heated

over e

ire

length.

Which one of

the following relationship

between nan c

boundary

Iayer thickness a) and the thermal

boundary

layer t c ) is

true?

a) 5.:> a

b)

5.:< a c)

a =

a r'" .

d) Cannot be predicted

2.18.

In

a spark

ignition

engine working

on

the

ideal

Otto

t t

om

pression

ratio

is

5.5.

The work output per cycle i.e., area

a g r a m )

is equal to

23.625x10YVcJ, where

Vc

is the dearance val e i m . The indicated mean

effective

pressure

is

a) 4.295 bar 50 bar

c)

86.870 bar

.

06.300 bar

2.19.

The

height

of the

down-sprue

i m and

its

cross-sectional area at

the

base

is

200

m m

2

The cross-sectio

ar

of

the

horizontal

runner is

also

200

m m

2

assuming

no losses, i ndi

:t

rrect

choice

for

the

t ime

in seconds)

required

to fill am old cavity of val m

6

m

3

Use g = 10 m/s

2

.

a) 2.67 c)

26.72

d) 84.50

2.20. For rigid w o r k material, negligible interface friction and no

red un dan t wo th

theoretically

maximum possible

reduction

in the wire

drawing

o

erati

·

+

b)

0.63

c) 1.00 d) 2.72

a) 5625 W-sec

c)

22500

W-sec

b) 8437 W-sec

d)

33750

W-sec


9/13

2. 2 3. Fi

tty

observations

of

a

production

operation revealed a

mean

cycle time

of 10

min.

the worker

was

evaluated to

be

performing

at 90

efficiency.

Assuming the

all

ow

ances

to

be

10 of the

n arm al

time, the standard time (in

seconds for

the

job

is

(a)

0.198

(b) 7.3 (c)

9.0

(d) 9.9

2.24. 3-2-1 method of location in

a

j ig or fixture

would

collectively r s t r i

piece

in

n degrees

of

freedom,

where

the

value

of

n

is

a) 6

b)

8

c)

9

~

2.25. In an NC machining operation, the tool has to be moved point

(7,2) along a circular

path with

center at (5,2). Before starti the peration, the

tool

is

at

(5,4).

The correct G

and

M code for this

motion is

(a) NOlO G03 X7.0 Y2.0 15.0 J2.0 (b) N r Y 2 . 0 15.0

J2.0

(c)

NOlO

GOl

X7.0

v2.0

15.0 J2.0

(d)

~

v2.0

15.0

J2.0

SE TION \

ThIS sect1 on con

s1sts of

TWEN TV quest1 on s

of

Fl s each. Attempt ANV Fl

FTE

EN

questions. Answers

must

be g1ven 1n the ~ v1ded.

3. Solve the d1fferent1al

equation, '

d y

- · (

1

4.

Motor 2000 rpm

15 N m


10/13

5

6

7

8.

9

Water (p

=

100

0 k

g/m

flows

horizontally through

a nozzle into

the atmosphere

under the con di ti on s given bel ow. (assume

steady

state flow).

~ . . : : . 2

[

At inlet:

At=

10- in

2

; Vt = 2m/sec; Pt=3x10s Pa(gauge)

At outlet: A

1

= 10-

4

m

2

; P

2

= Paun

D eterm me the external h on zan tal force needed

to

keep the

~ .

A number of cold

rolling

passes

are

requ1red 1n a two-high Ill to reduce

the thickness

of

a plate fi om 50 m m to 25 mm. The m 1s 700 m m and

the

coeffi

c1

en

t

of

fi 1

ct1

on

at

the

roll

work

1n

terface 1 0 . 1 req

u1 red

that

the

draft 1n each pass must be the sam e. Assu

and back tens1 ons,

determ me (a) the m 1n 1mum number of passes r

o

n d (b) the draft 1n each

pass. ~ ) . , . . _....

Steam

at

300 kPa and 500°C (h = ~ ~ r enters a steam

turbme

and

exits

at atm aspheric pressure

and

h =

3175.8

kJ/kg). Heat losses in the

turbine

are

50 kW

and

the m a flo , is 0.25 kg/s.

determine

the

power

output of the turbine

i

kinetic es are neg gi b e.

Two solid workp1eces, 1) l i 1th rad1us Rand 11) a cylinder With diameter

val um e. Show

that II

al work

-p1

ece

Will

solid 1y faster than the sp hen cal

equal

to

1ts h e 1 g h v o sand cast.

Both

work-pieces have the same

work-piece.

ass

system 1 shown

1n the figure.

The spn n g stif fness 1

k,

the

VIscous

damp

mg coeffi

c1

en

t 1 c.

the

system 1 subJected

to

a

~ l ~ s h o w n .

Write

the equations of motion which are needed to

1

o need

to determined

x.)

x=O

I

r- x

k

c

1-0 - o cos


11/13

11. Use the area

moment

method to find the vertical deflection of the uniform beam

AB

at

the following

points:

12.

13.

14.

15.

(a) middle

of the beam

(point 0

(b) Ieft end of the beam (point A)

The flexural

rigidity

of the beam is EI

0

I•

~ : • ~ 1 •

Tool hfe test1ng on a

lathe

u ~ e r dry cuttmg

c ~ n d t o n s

gavQ C of Taylor

tool life equat1on as 012 and 130 m/mm, respect1vele n

't'=

oolant was used,

C

mcreased

by

10 .

Fmd

the

percent

mcrease

1n

to

I

th the

use

of

coolant

at

a cutting speed of90 m/mln.

~

Identical straight turnmg operation was r i : J ~ two tools:

8-8-5-5-5-

25-0 ASA)

and

8-8-5-5-7-30-0 ~ t

the

first

tool will

g1ve

better

surface fin 1 h 1n terms of peak-to-vall ' •

Water flows through a

0.6

m d DO m long pipe from a 30 m overhead

tank

to

a

village.

Find the

di ar in

liters)

at

the

village

(at

ground

level),

assummg a Fannmg

0.04 and 1gnonng mmor losses due to

bendsetc. V

A com pos1te

wall, length normal

to the plane

of

paper, 1s msulated at

the top and

shown

1n the figure. I t 1 com pn sed of four d fferen t

matenals

A v .

+

f

I r s u : e ~

t

Ho

~ .

H•=Ho D

i-rh'7 7c..,...,+r-:l Li He

Tz hz

The dimensions are:

HA

= Ho

=3m,

Hs

=He=

1.5

m,

L

1

= L

3

= O.OSm, L

2

=

0.1

m

The

thermal conductivity

of the

materials

are:

KA

= K

0

= 50

W/m-K,

K

B

=

10W/m-k, Kc=

1

W/m-k.

The

fluid

temperatures

and heat

transfer coefficients (see

figure)

are: T

1

=

?nnoc: h = W/m

2

-K. ? ~ o c : ho= 1n W/m

2

-K.


12/13

Assuming one-dimensional conduction,

a) sketch the thermal d rcui t of the system, and

b) determine the rate of heat transfer through the wall.

16

A Brayton cyde air

standard)

has a pressure ratio of 4 and inlet condition of

one standard atmosphere pressure and 27 °C Find the air flow rate req ui r

100

kW power output

i

the maximum temperature in the cyde is

Assume

y

1 4 and p = 1 0

kJ/kg-K.

17.

lB.

a)

19. The 2 kg mass C

movi

5 m s

c

B

m echam c has an

en

gm e from a 1970 mode car which works on the basis

of

Otto cycle. The engine displaces l .B liters, has a com pression ratio

of

10 2: 1 and

has six cylinders. The pistons

in

the original engine

are

120 m m

in diameter.

The

mechanic bores the cylinder and rep I aces the piston with new pi stan s that are 2

m m larger in

diameter

than the originals.

a)

Keeping all other factors same,

what will be the percentage change

in

power output? b) By what percentage

wi

II

the engine efficiency change?

21. A company is offered the foilowing price breaks for order quantity


13/13

22.

0 100

150

101 and

above

100

Order

cost is

Rs

60

per order

whi I e

the holding

cost is

10

of

the p

urc

·ce.

~ ~ i ~ e ; m

ine

the

economic

order quantity (EOQ) i f the annual r e q u i

1 0

The shaft shown is supported on bearings

at

A and B.

i a

hree

eccentric

masses (each of mass

m)

in planes parallel to

x-y

C, D and E

the

eccentricity of mass

at

C

is

e and eccentricity of es D

and

E

is

~

n di cate

the angular

re to

that

of mass

at C

p

vide

static balance. AI so

g reactions

at

A and B for

twad mechanical engineering

Documents