(^42) A Textbook of Engineering Mechanics
- A square ABCD of 60 mm side is subjected to force of 10 N, 20 N, 30 N and 40 N along
the sides AB, AC, BD and AD respectively. Find magnitude. direction and position of the
resultant force with respect to A.[Ans. 75.4 N; 87.7° ; 16.88 mm] - A compound lever shown in Fig. 3.22 is required to lift a load of 9 kN with an effort P.
Fig. 3.22.The dimensions are AF 1 = 450 mm ; F 1 B = 50 mm ; BC = 100 mm ; CD = 300 mm ; DF 2
= 75 mm. Find the effort required to lift the load. [Ans. 200 N]QUESTIONS
- What is meant by moment of a force? How will you explain it mathematically?
- How will you represent the moment of a force geometrically?
- Explain clearly the difference between clockwise moments and anticlockwise moments.
- State clearly the law of moments.
- State the Varignon’s principle of moments.
- What is a lever? Distinguish clearly between a simple lever and a compound lever.
- What do you understand by the term ‘leverage’? Explain its usefulness.
OBJECTIVE TYPE QUESTIONS
- The moment of a force about any point is geometrically equal to... area of the triangle
whose base is the line representing the force and vertex is the point about which the
moment is taken.
(a) Half (b) Same (c) Twice (d) None of these - In a clockwise moment, we actually use wall clock in order to know the time for which
the moment is applied.
(a) Right (b) Wrong - If a number of coplaner forces are acting simultaneously on a particle, the algebraic sum
of the moments of all forces about any point is equal to the moment of their resultant
force about the same point. This principle is known as
(a) Principle of moments. (b) Principle of levers
(c) None of them - In the study of levers, we ..... the principle of moments.
(a) Use (b) Do not use - In a compound lever, the leverages of all the simple levers is
(a) Added (b) Subtracted (c) Multiplied (d) Divided - The term ‘leverage’ and ‘mechanical advantage’ in a compound lever have got the same
meaning.
(a) Agree (b) Disagree
ANSWERS
- (a) 2. (b) 3. (a) 4. (a) 5. (c) 6. (a)
Top