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VELALAR COLLEGE OF ENGINEERING AND TECHNOLOGY
Department of MECHANICAL ENGINEERING
[2012- 2013]
Class: MEC02 & CEG02
MODEL EXAMINATION
Subject Name : ME 2151ENGINEERING MECHANICS
Date: 29.05.2013 Max. Marks : 100
Time: 9.15 am12.15 pm Duration: 3 Hrs.
Part A (10 x 2 = 20 Marks) Answer all questions
1. Two vectors A and B are given as A = 2i+3j+kandB=3i+3j+4k.
Determine the cross product and the unitvector along it.
2. Find the resultant of an 800N force acting towardseastern
direction and a 500N force acting towardsnorth-eastern
direction.(45
0to the 800N force)
3. Give the equations which express the conditions for
theequilibrium of rigid body.
4. Two forces F1=5i and F2=8.66j pass through a pointwhose
coordinates are (2,1)m. Calculate the moment of
the forces about the origin.
5. Explain the term briefly the radius of gyration of
anarea.
6. State parallel axis theorem with a simple sketch
forillustration.
7. A body is dropped from rest. Determine(i)the timerequired for
it to acquire a velocity of 16m/s and (ii)thetime needed to
increase its velocity from 16m/s to
23m/s.
8. A mass of 50kg has an initial velocity of 15m/shorizontally
on a smooth surface. Determine the valueof the horizontal force
that will bring the mass to rest in
4 seconds.
9. What is meant by impending motion when a bodymoves over
surface with friction?
10. The angle of rotation of a rigid body is given by
theexpression =t3-3t2+4t+8 where is in radians and t isin seconds.
Find the angular velocity when t=3 seconds.
Part B (5 x 16 = 80 Marks) Answer all questions
11. a Three forces act at a point A on a block as shown infig.1.
The directions of the 300N forces may vary but
the angle between these 300N forces is always400.Determine the
value of the angle for which theresultant of the forces acting at A
is directed parallel to
the plane b-b.
(OR)
11. b Find the magnitude of the concurrent forces such that
ifthey act at right angles, their resultant is 10 and if theyact at
60
0their resultant is 13.
12. a Two wires AC and BC are attached to the top of the
pole CD as shown in Fig.2. The force exerted by the
pole is vertical. The 2500N force applied at point C is
horizontal and also parallel to the Z axis ( =900
).Determine the tension in each cable.
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(OR)
12. b Determine the horizontal and vertical components of
the reactions for the beam loaded as shown in Fig.3.Neglect the
weight of the beam.
13. a Locate the centroid of the plane shown in Fig.4
(OR)
13. b Find the moment of inertia of the shaded area shown in
Fig5. About the horizontal and vertical centroidal axes.
The width of the hole is 200mm.
14. a A fireman holding a nozzle at a horizontal distance of4.8m
from a vertical wall, wishes to send a jet of water
through a small window in the wall located 3.6mvertically above
the nozzle as shown in Fig 6.If the
inclination of the jet with the horizontal is 600,
Determine the required velocity of the jet at the exit ofthe
nozzle.
(OR)
14. b A 2000 kg automobile driven down a 5 inclined planeat a
speed of 100km/h when the brakes are applied
causing a constant total breaking force( applied by theroad on
the tires) of 7 kN. Determine the distance
travelled by the automobile as it comes to stop.
15. a A flat belt develops a tight side tension of 2000Nduring
power transmission. The coefficient of friction
between the pully and the belt is 0.30. The angle of lap
on smaller pully is 1650
and the belt speed s 18 m/s.Determine the power that can be
transmitted, if the belt
is assumed to be perfectly elastic and massless.16
(OR)
15. b A flywheel starts rotating from rest and is given an
acceleration of 3 rad/s2
i) Find the angular velocity and the speed in rpm after
90 seconds8
ii) If the flywheel is brought to rest with a uniform
angular retardation of 2 rad/s2, determine the time taken
by the flywheel in seconds to come to rest8
