RE.IB.Tech. DEGREE EXAMIN~ON~ NO~MBERlDECE1.fBER 2005.

[; SecondSemester

Civil Engineering

(Common to an branChes)'"'.'..

GE 1151 ~ ENG~ERING MECHANICS

Time: Three hours Maximum: 100 marks

'Answer ALL questions.'

PART A - (10 x 2 = 20 marks)

1. State the principle of~~s&ibility.:,.:

2. Three coplanar forces of magnitude P Newtons each are acting" on a particle. Iftheir fuleg' fA'aCtion '~;"'~:~8!t Witb'~"'~ttiat' the 'fOrcesare in equilibrium. ," " : " , "

3. State the Varignon's theorem.

4. Find the moment of ~ force of 15 N acting along the positive direction 'ofX-axis about the point A (2, 3) .

5., .' . .'

Distinguish between centroid and centre ,of,gravity.

6. Define product of inertia, ' . ,.. ..~:' ...,~..12:

7. Explain briefly. the two types of collision." '

8. If the distance x em travelled by a particle in t-secondt/"is given hyx = 2Ot2 + 50t + 19, find the velocity and acceleration after 3 seconds.

9. State the laws of friction.

10. Briefly explain "step of the belt" in belt drives.

PART B .......(5 x 16 = 80 marks)11. For a section given in fig. 1; ':,:

(i) Locate the horizontal oontroidal ~X.

(ii) Locate the vertical centrmdal axis-Y.': ,(8)

(8)

ft(

..L '~."

1K:< ;5'0 ~,,

LL J)/rflEN.$/O/VS ~E 4-50tv/M, ' ..... 5"0 ILN I'

~' 4-75'"

" !to: ,-,.... r"2-Oe> ~..f. "

r Itoo ~r

.:d.

fig. 1

12. (a) A pole AB, 6 m long is, held by three guy wires, as ;Sbuwn'lm fig. ;2.Determine the moment about each of the coordinate axes of the :force

'u":"i",~ ..,~~~Y;,~:,,~~W~,~~:Thetensio~'Tin~e~~i~"'~~;tc;~

. l,

-,

~----~----_.~----~~----~~,XA.

",

"" fig. 2Or

2 D 134

(b) Determine the magnitude and t:lireclion of a single forCeP .hich keeps inequilibrium. The system M"forees acting is shown ih fig. 3. (16)

. fig. 313. (a) Find the reactions at supports A and B of the beam as shown in fig. 4.

usr

,ng.4Or

(b) F{)~cesof magnitudes 1, 2, 3, 4 and 2.J2 Newtons act respectively alongthe sides AB, Be, CD, DA and the diagonal AC .of the square ABeDwhose side is 3 m. Show that their resultant .is rouple and 6:rid itsmoment. . . (16)

14. (a) A force F = 30 N acts parallel to the inclined plane as it accelerates ablock of mass m :: 2 kg upto the 30Q incline with a coefficient of kineticfriction IJK = 0.3 as shown in fig. 5. A spring whose force constant 'K is40 Nm -1 is attached to the block' which starts from rest at a positionx = 0 , where the spring is unstressed. Find the speed of the block aftertravelling 0.2 in up the incline? Use work energy method. (16)

~.,

fig. 5Or

3 DIM

(b) (i) AstoJle isthxown \1p'ward,S from the top ()f_' tower, 7(),mhighwith avelocity of 19..2 mJS. Determine its position and velocity whent = 6 sec. (8)

(ii) An elevator is required to lift' a body of mass 65 kg. Find theacceleration of the elevator, which could cause a pressure of 800Newtons onthEdloor~ . (8)

15. (a) Block A weighing 1500 N is to be raised by means of 15 wedge as shownin fig. l5.Assume the-coefficient of friction between all contact surfaces be0.2. Weight of the block B is 500 N. Determine the minimum forcerequired tomove the block A upwards. '(16)

. '', ~, fig. ~ .

...;"~",:,:"".,.... ;!~;:.~~,,:,~~:,::,:.;.,.;:.:~~~,t~L.~:ip;i~' -. : ..... , ., ;.;''i;'''' -: ': /" .,' . ".!~~.. ._'.

(b) A reciprocating engine mechanism is shown in fig. 7. The crank OA is oflength 150 mm .and rotating' at 600 rpm. The connecting rod AB is700 nun long. Find ';.i'.(i) The ~v~~t~9f~:~~~. , .. ' . (5);(ii) The velocity'l)fpistOn H", ":::},.:':. ,',i." .."~ '": ,: ' , (5).(iii) , 'The vei&cit}Vaf;poih(C"b~ ':thk e&tm~ing: tod':"ata distance of

200mmfromAwhen8=45 . ;,',,