# Dynamics of Machinery (2161901) MCQ

### MCQs of Balancing of Rotating Masses

MCQ No - 1

#### The balancing of rotating and reciprocating parts of an engine is necessary when it runs at

(A) slow speed
(B) medium speed
(C) high speed
(D) None of the above

C
MCQ No - 2

#### The static balancing is satisfactory for low speed rotors but with increasing speeds, dynamic balancing becomes necessary. This is because, the

(A) unbalanced couples are caused only at higher speeds
(B) unbalanced forces are not dangerous at higher speeds
(C) effects of unbalances are proportional to the square of the speed
(D) effects of unbalances are directly proportional to the speed

C
MCQ No - 3

#### A system in dynamic balance implies that

(A) the system is critically damped
(B) there is no critical speed in the system
(C) the system is also statically balanced
(D) there will absolutely no wear of bearings

C
MCQ No - 4

#### A disturbing mass ${m}_{1}$ attached to a rotating shaft may be balanced by a single mass ${m}_{2}$ attached in the same plane of rotation as that of ${m}_{1}$ such that

(A) ${m}_{1}.{r}_{2}={m}_{2}.{r}_{1}$
(B) ${m}_{1}.{r}_{1}={m}_{2}.{r}_{2}$
(C) ${m}_{1}.{m}_{2}={r}_{1}.{r}_{2}$

B
MCQ No - 5

#### For static balancing of a shaft

(A) the net dynamic force acting on the shaft is equal to zero
(B) the net couple due to the dynamic forces acting on the shaft is equal to zero
(C) both A. and B
(D) none of the above

A