R.No
B.E/B. Tech( Full Time) END SEMESTER EXAMINATIONS, NOV/DEC 2013
SECOND SEMESTER - Regulation 2012
(Common to Agri/Civil/Mech/Geoinfor/Matsci/Manuf/lnd/Print/Mining/EEE)
G E 8251 ENGINEERING MECHANICS
Time : 3 hr
Max Mark : 100
Part A ( 1 0 X 2 = 20 mark)
8. A force of 1 k N inclined upward at an angle of 45 degrees with x-axis acts at a point <2 m, 2 m). Using
Varignon theorem find the moment of the force about the origin.
2. Determine the resultant of spatial forces F = 600 N , F = 500 N , and F = 200 N. Find also its
x
y
z
inclination with origin
3. What is the difference between couple and moment?
4. There is a clockwise couple of 40 Nm on the x-axis Its centre is located at 5 m from the origin. There is
another counterclockwise couple of 70 Nm aiong y-axis and its centre is 2m from the origin. What is the
resultant effect of these couple at the origin.
5. What is the height of centroid of a symmetrical trapezium of height 3 m from its base, if its top width is
3 m and bottom width is 6 m?
6. A circular disc of radius 650 mm and weight 40 N has its centroid at the origin. What is its polar mass
moment of inertia?
7. The acceleration of a passenger lift is 1.5m / s . Starting from the rest, find the time required for the lift
2
to descend 30 m.
8. A car is moving at uniform speed of 15 m /s on a circular road of radius 300 m. What is the total
acceleration of the vehicle?
9. A body of weight 10 N moves under the action of force F. The x component and y component of
acceleration of the body are 3 m Is and 4 m Is respectively. Find the force F.
2
2
10. A force of 40 N is required to move a body over a distance of 5 m in 2 seconds. What is the work done
and power spent?
Part-B( 5X16 = 80 mark)
11. Two horizontal beams AB and CD are supported as shown in Figure Q 11(a). An external inclined
force of 2 k N acts at B. All the hinges are smooth so that the hinge reactions at A and C are horizontal
and the hinge reaction at D is inclined at 30 to the horizontal. Calculate the hinge reactions and-roller
0
reactions.
Contd..2
-2-
2kN
P
30*
•
1m
1m
1m
1m
Fig Q 11(a)
12 (a) A cubical block of wood of weight 200 N is hinged at A and rests on a roller at B as shown in Fig
Q12(a). It is pulled by a string attached at D at an angle 3 0 with horizontal. Determine the force P
0
required to just lift the block off the roller
30"
a
W
= 200 N
B
mnrrrn
a
Fig Q 12(a)
OR
12(b) Two identical rollers each weighing 500 N rest on an inclided plane and and are supported by
vertical wall as shown in Fig 0.12(b). Assuming surfaces of contact are smooth, determine the wall reaction
at P , floor reaction at R and S and reaction of the one roller against other.
500 N
y
500 N
Roller A
Roller 4
Fig Q 12(b)
Contd..3
-33(a) Deteimine the x and y coordinate of the centroid of the shaded area shown in the Figure Q 13(a)
T
0.25
-t
0.5 m
FigQ13(a)
OR
3(b) The cross section of a bearing block is shown in the Figure Q13(b) by the shaded area . Calculate the
loment of inertia of the section about its base a-a.
I
100
mm
m
mm
300
FigQ13(b)
4(a) A car is driven at a speed of 70 km/ h on a curved road of 200 m The speed of the car is reduced to 40
m /hr in 10 seconds after the application of the brake. Assuming uniform deceleration, find the following:
1. normal, tangential and total accelerations of the car before braking
2. normal, tangential and total accelerations of the car after braking
OR
4(b) A block of mass 25 kg rests on an inclined plane of 30 deg to the horizontal. The coefficient of kinetic
iction between the plane and the block is 0.48. Determine the force P parallel to the incline to be applied
le block •to give it an acceleration of 5m Is in the downward direction parallel to the incline.
2
Contd..4
-4-
*
5(a) Two blocks A and B of weight 600 N and 1200 N respectively rest against a wall and a floor as shown
I Figure Q15(a). The coefficient of friction between the blocks , between the floor and block and between the
'all and block are 0.2. Determine minimum horizontal force P necessary to hold the block in equilibrium.
600
60
1200 N
Fig Q15(a)
OR
15(b) A flywheel of mass 5000 kg and radius of gyration 1 m loses its speed from 400 rpm to 200 rpm in
160 s. Calculate the following:
1. retarding torque
2. change in the kinetic energy during the period
3. change in the angular momentum.
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