15. A steel joist has a span of 6 m and the ends are simply supported. The joist has a mass of 52 kg/m and the second moment of area of the cross-section is 120 x 10-6 m4. A load of 3 t is carried at a point 2-4 m from one support. Find from first principles the frequency of the natural transverse vibrations of the joist, if the effect of its own mass is neglected. Then find the approximate frequency when the mass of the joist is taken into account. (I. Mech. E.) (Ans: 7-01 Hz: 6.82 Hz [8= 5.09 mm: A 0-3585 mm])

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
icon
Related questions
Question

questions 15&18. step by step solutions.

15. A steel joist has a span of 6 m and the ends are simply supported. The
joist has a mass of 52 kg/m and the second moment of area of the cross-section
is 120 x 10-6 m². A load of 3 t is carried at a point 2-4 m from one support.
Find from first principles the frequency of the natural transverse vibrations
of the joist, if the effect of its own mass is neglected. Then find the approximate
frequency when the mass of the joist is taken into account. (I. Mech. E.)
(Ans. 7.01 Hz; 6-82 Hz [8 = 5.09 mm; A = 0.3585 mm])
16. A beam with second moment of area of cross-section 8 x 10-6 m and
of mass 18 kg/m is simply supported at the end of a 3.6 m span and it carries a
body of mass 250 kg at the centre. Find the frequency of transverse vibrations.
(I. Mech. E.)
(Ans.: 12.2 Hz [8: 1.49 mm; A = 0.241 mm])
=
17. Two parallel steel beams span an opening of 6 m and jointly support
a central load of 3 t. Each beam has a mass of 45 kg/m run and the moment
of inertia of the section is 86 x 10-6 m¹. Assuming the beams are simply
supported at the ends, calculate the natural frequency of the transverse vibra-
tions. (U. Lond.) (Ans.: 7-72 Hz [8= 3-85 mm; A = 0.433 mm])
18. A small, imperfectly balanced machine is mounted on a rigid horizontal
plate, supported on four vertical legs each 28 mm outside diameter, 25 mm
inside diameter and 0.9 m long, rigidly welded to the plate but having their
other extremities always position fixed but direction fixed or not at will. If
the effective mass of the assembly is 45 kg, find the five lowest machine speeds
which would give resonance corresponding to the five different conditions of
the legs. (U. Lond.)
(Ans. 9.06, 8-16, 7-17, 5-99, 4-53 Hz)
Transcribed Image Text:15. A steel joist has a span of 6 m and the ends are simply supported. The joist has a mass of 52 kg/m and the second moment of area of the cross-section is 120 x 10-6 m². A load of 3 t is carried at a point 2-4 m from one support. Find from first principles the frequency of the natural transverse vibrations of the joist, if the effect of its own mass is neglected. Then find the approximate frequency when the mass of the joist is taken into account. (I. Mech. E.) (Ans. 7.01 Hz; 6-82 Hz [8 = 5.09 mm; A = 0.3585 mm]) 16. A beam with second moment of area of cross-section 8 x 10-6 m and of mass 18 kg/m is simply supported at the end of a 3.6 m span and it carries a body of mass 250 kg at the centre. Find the frequency of transverse vibrations. (I. Mech. E.) (Ans.: 12.2 Hz [8: 1.49 mm; A = 0.241 mm]) = 17. Two parallel steel beams span an opening of 6 m and jointly support a central load of 3 t. Each beam has a mass of 45 kg/m run and the moment of inertia of the section is 86 x 10-6 m¹. Assuming the beams are simply supported at the ends, calculate the natural frequency of the transverse vibra- tions. (U. Lond.) (Ans.: 7-72 Hz [8= 3-85 mm; A = 0.433 mm]) 18. A small, imperfectly balanced machine is mounted on a rigid horizontal plate, supported on four vertical legs each 28 mm outside diameter, 25 mm inside diameter and 0.9 m long, rigidly welded to the plate but having their other extremities always position fixed but direction fixed or not at will. If the effective mass of the assembly is 45 kg, find the five lowest machine speeds which would give resonance corresponding to the five different conditions of the legs. (U. Lond.) (Ans. 9.06, 8-16, 7-17, 5-99, 4-53 Hz)
Expert Solution
steps

Step by step

Solved in 4 steps with 17 images

Blurred answer
Knowledge Booster
Free Undamped Vibrations
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.
Similar questions
  • SEE MORE QUESTIONS
Recommended textbooks for you
Elements Of Electromagnetics
Elements Of Electromagnetics
Mechanical Engineering
ISBN:
9780190698614
Author:
Sadiku, Matthew N. O.
Publisher:
Oxford University Press
Mechanics of Materials (10th Edition)
Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:
9780134319650
Author:
Russell C. Hibbeler
Publisher:
PEARSON
Thermodynamics: An Engineering Approach
Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:
9781259822674
Author:
Yunus A. Cengel Dr., Michael A. Boles
Publisher:
McGraw-Hill Education
Control Systems Engineering
Control Systems Engineering
Mechanical Engineering
ISBN:
9781118170519
Author:
Norman S. Nise
Publisher:
WILEY
Mechanics of Materials (MindTap Course List)
Mechanics of Materials (MindTap Course List)
Mechanical Engineering
ISBN:
9781337093347
Author:
Barry J. Goodno, James M. Gere
Publisher:
Cengage Learning
Engineering Mechanics: Statics
Engineering Mechanics: Statics
Mechanical Engineering
ISBN:
9781118807330
Author:
James L. Meriam, L. G. Kraige, J. N. Bolton
Publisher:
WILEY