Theory Of Machine(Mechanical Engineering ) Questions and Answers

Question 1. The lower pairs are _________ pairs.
  1.    Self-closed
  2.    Force-closed
  3.    Friction closed
  4.    None of these
Explanation:-
Answer: Option A. -> Self-closed
Question 2. In considering friction of a V-thread, the virtual coefficient of friction (μ1) is given by
  1.    μ1 = μsinβ
  2.    μ1 = μcosβ
  3.    $${\mu _1} = \frac{\mu }{{\sin \beta }}$$
  4.    $${\mu _1} = \frac{\mu }{{\cos \beta }}$$
Explanation:-
Answer: Option D. -> $${\mu _1} = \frac{\mu }{{\cos \beta }}$$
Question 3. In a coupling rod of a locomotive, each of the four pairs is a ________ pair.
  1.    Sliding
  2.    Turning
  3.    Rolling
  4.    Screw
Explanation:-
Answer: Option B. -> Turning
Question 4. A kinematic chain is known as a mechanism when
  1.    None of the links is fixed
  2.    One of the links is fixed
  3.    Two of the links are fixed
  4.    None of these
Explanation:-
Answer: Option B. -> One of the links is fixed
Question 5. A pantograph is a mechanism with
  1.    Lower pairs
  2.    Higher pairs
  3.    Rolling pairs
  4.    Turning pairs
Explanation:-
Answer: Option A. -> Lower pairs
Question 6. If two moving elements have surface contact in motion, such pair is known as
  1.    Sliding pair
  2.    Rolling pair
  3.    Surface pair
  4.    Lower pair
Explanation:-
Answer: Option D. -> Lower pair
When two elements of a pair have a surface contact when relative motion takes place and the surface of one element slides over the surface of the other, the pair formed is known as lower pair.
Question 7. The primary unbalanced force due to inertia of reciprocating parts in a reciprocating engine is given by (where m = Mass of reciprocating parts, $$\omega $$ = Angular speed of crank, r = Radius of crank, $$\theta $$ = Angle of inclination of crank with the line of stroke and n = Ratio of the length of connecting rod to radius of crank)
  1.    $${\text{m}}{\omega ^2}{\text{r}}\sin \theta $$
  2.    $${\text{m}}{\omega ^2}{\text{r}}\cos \theta $$
  3.    $${\text{m}}{\omega ^2}{\text{r}}\frac{{\sin 2\theta }}{{\text{n}}}$$
  4.    $${\text{m}}{\omega ^2}{\text{r}}\frac{{\cos2\theta }}{{\text{n}}}$$
Explanation:-
Answer: Option B. -> $${\text{m}}{\omega ^2}{\text{r}}\cos \theta $$
Question 8. The secondary unbalanced force due to inertia of reciprocating parts in a reciprocating engine is given by (where m = Mass of reciprocating parts, $$\omega $$ = Angular speed of crank, r = Radius of crank, $$\theta $$ = Angle of inclination of crank with the line of stroke and n = Ratio of the length of connecting rod to radius of crank)
  1.    $${\text{m}}{\omega ^2}{\text{r}}\sin \theta $$
  2.    $${\text{m}}{\omega ^2}{\text{r}}\cos \theta $$
  3.    $${\text{m}}{\omega ^2}{\text{r}}\frac{{\sin 2\theta }}{{\text{n}}}$$
  4.    $${\text{m}}{\omega ^2}{\text{r}}\frac{{\cos2\theta }}{{\text{n}}}$$
Explanation:-
Answer: Option D. -> $${\text{m}}{\omega ^2}{\text{r}}\frac{{\cos2\theta }}{{\text{n}}}$$
Question 9. The sensitiveness of the governor __________ as the speed range decreases.
  1.    Remains unaffected
  2.    Decreases
  3.    Increases
  4.    None of these
Explanation:-
Answer: Option C. -> Increases
For a given lift of the sleeve, the sensitiveness of the governor increases as the speed range decreases.
Question 10. The velocity of piston in a reciprocating steam engine is given by (where $$\omega $$ = Angular velocity of crank, r = Radius of crank pin circle, $$\theta $$ = Angle turned by crank from inner dead center and n = Ratio of length of connecting rod to the radius of crank)
  1.    $$\omega {\text{r}}\left( {\sin \theta + \frac{{\sin 2\theta }}{{\text{n}}}} \right)$$
  2.    $$\omega {\text{r}}\left( {\cos\theta + \frac{{\cos2\theta }}{{\text{n}}}} \right)$$
  3.    $${\omega ^2}{\text{r}}\left( {\sin \theta + \frac{{\sin 2\theta }}{{\text{n}}}} \right)$$
  4.    $${\omega ^2}{\text{r}}\left( {\cos\theta + \frac{{\cos2\theta }}{{\text{n}}}} \right)$$
Explanation:-
Answer: Option A. -> $$\omega {\text{r}}\left( {\sin \theta + \frac{{\sin 2\theta }}{{\text{n}}}} \right)$$
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