ME2151 Engineering Mechanics Question bank

Engineering Mechanics
QUESTION BANK
PART B
1.The sum of two concurrent forces P and Q is 270N and their resultant is 180N. The angle between the forces
P and and the resultant R is 90˚. Find the magnitute of each force and angle between them.
(Ans P=75N,Q=195N ,Angle=112˚)
2.Two forces P and Q act on a bolt as shown in the fig a .Determine the resultant force
(Ans R=88.1N Angle=8˚)
Q=30N
P=60N
25˚
10˚
fig a
3.The resultant of two concurrent forces is 1500N and the angle between the forces is 90˚. The resultant
makes an angle of 36˚ with one of the force .Find the magnitude of each force
(Ans P=1213N Q=881.26N)
4.An electric light fixture weighing 15 N hangs from a point C, by two strings AC and BC.AC is inclined at
60˚ to the horizontal and BC at 45˚ to the vertical as shown in the fig b. Determine the forces in the strings.
( Ans T1=7.75N,T2=10.98N)
O A
60◦
B
45°
C
15N Fig b
5. A lamp weighing 10N is suspended from the ceiling by a chain. It is pulled by a horizontal chord until the
chain makes an angle of 60˚ with the ceiling as shown in the fig c. Find the Tension in the chain.
60˚
chain
O Chord Figc
10N
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6. A string PQRS attached to two fixed point P and S has two equal weight of 500N attached to Q
and R. The weight rests with the portions PQ and RS inclined at angles 30˚ and 60˚ respectively to the
vertical as shown .Find the tensions in string if the inclination of the position QR with the vertical is 120˚.
Fig d
Under Moments
7. A loaded cantilever beam is shown in fig a. Find the moment of force about O. (Ans: 21545.94Nm)
1500N 750N
45˚
9m
16m
8. A force F=6i-3j-4k N is acting at a point P whose position vector from the origin O is 8i+6j-4k mm.
Find the moment of the force about the origin. (Ans:36i+8j-60k N-mm)
9. A force of 200N is directed along the line drawn from the point A (8,2,3)m to the point
B(2,-4.4,7.8)m.Find the magnitude of the force about Z axis. (Ans: 784 Nm CCW)
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Coplanar Forcer(Resolution and Composition of forces)
10. Three forces of magnitude 40KN, 15KN and 20KN are acting at a point O as shown in the fig.The
angles made at by 40KN,15KN, and 20KN forces with X axis are 60˚ ,120˚ ,240˚ respectively.Determine
the Magnitude and direction of the resultant force (Ans: R=30.14KN,è = 85˚)
Y
15KN 40KN
120˚
60˚
240˚ X
20KN
11 If five forces act on a particle as shown in the figure and if the algebraic sum of the horizontal
components of all forces is -300KN. Calculate the magnitude of force F and the resultant of all the forces.
Y
200KN 250KN
F 200KN
3
4
30˚ 45˚
75KN X
Force in Space
12. A force of 500N of angle 60˚ ,45˚ ,120˚ respectively with x,y and z axes. Find Fx , Fy and Fz of the
force. ( Ans F = 250i +353.55j -250k)
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13. Determine the resultant of the three forces F1 = 2.0i+3.3j-2.6k, F2=-1i+5.2j-2.9k and F3=8.3i-6.6j-5.8k
Which are concurrent a the point(2,2,-5).The forces are in Newton and the distances are in metre.
14. Members OA,OB and OC forms a three member truss. A weight of 10KN is suspended at the joint
O.Determine the magnitude and nature of forces induced in each the members of the frame.
Support and Reactions
````
15. Determine the reactions at A and B.
50KN 20KN 30KN
60˚ 40˚
` A B
C D E
20 cm 40cm 70cm 40cm
16 A beam AB of 6m long is loaded as shown in the figure below. Determine the reactions at A and B.
10KN 20KN
1.5KN/m
A 140˚ B
6m
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17. Determine the reaction at the two ends of the beam
50N 30N 18N 6N
70˚ C D 30˚ E
A B
200mm 150mm 600mm 150mm
Knife Edge
18. Calculate the magnitude of the resultant force about the corner B.
4KN
A 15KN 60˚
B
5KN 10 ┌2 KN 2.5m
B C
3m
19. A rigid bar is subjected to a system of parallel forces. Reduce the system to
i) single force ii) Single force moment about A iii) Single force moment about B.
16N 62N 10N 30N
40cm 30cm 50cm
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20. Four forces are acting along the side a square ABCD of side 2m as shown below. In addition another
force is acting along the diagonal CA. Calculate the resultant moment about the corner B.
A 2 KN B
3 KN 8KN 4.2KN
D C
2.8KN
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