1. For a kinematic chain to be considered as mechanism
a) two links should be fixed
b) one link should be fixed
c) none of the links should be fixed
d) there is no such criterion
Explanation: If one of the links of the constrained chain is fixed, it results into mechanism.
2. An eccentric sheave pivoted at one point rotates and transmits oscillatory motion to a link whose one end is pivoted and other end is connected to it. This mechanism has
a) 2 links
b) 3 links
c) 4 links
d) 5 links
Explanation: Eccentric sheave is equivalent to 2 links, 1 link is due to oscillatory link, and one is fixed link.
3. Whitworth quick return mechanism is obtained by inversion of
a) slider crank mechanism
b) kinematic chain
c) five link mechanism
d) roller cam mechanism
Explanation: slider crank mechanism
4. Scotch yoke mechanism is used to generate
a) Sine functions
b) Square roots
c) logarithms
d) inversions
Explanation: In Scotch Yoke mechanism, the constant rotation of the crank produces harmonic translation of the yoke. Its four binary links are:
1. Fixed link
2. Crank
3. Sliding Block
4. Yoke.
5. Which of the following are inversions of a double slider crank chain?
1. Whitworth return motion 2. Scotch Yoke
3. Oldham’s Coupling 4. Rotary engine
Select correct answer using the codes given below:
Codes:
a) 1 and 2
b) 1, 3 and 4
c) 2 and 3
d) 2, 3 and 4
Explanation: Double slider crank mechanism
It has four binary links, two revolute pairs, two sliding pairs. Its various types are:
1. Scotch Yoke mechanism
2. Oldhams Coupling
3. Elliptical Trammel.
6. Oldham’s coupling is used to transmit power between two parallel shafts which are slightly offset.
a) True
b) false
Explanation: It is used for transmitting angular velocity between two parallel but eccentric shafts.
7. In Oldham’s coupling the condition for maximum speed ratio is
a) w1cosα/W
b) w1sinα/W
c) w1/W = 1/cosα
d) w1/W = 1/sinα
Explanation: w1/W = cosα/1 – cos2ϴsin2α
For maximum speed ratio cos2ϴ = 1
Therefore, w1/W = 1/cosα
8. The relative acceleration of two points which are at variable distance apart on a moving link can be determined by using the
a) three centers in line theorem
b) instantaneous centre of rotation method
c) Coriolis component of acceleration method
d) Klein’s construction
Explanation: The relative acceleration of two variable points on a moving link can be determined by using the instantaneous centre of rotation method.
9. What is the number of instantaneous centres of rotation for a 6-link mechanism?
a) 4
b) 6
c) 12
d) 15
Explanation: N = n(n – 1)/2 = 6 x (6 – 1)/2 = 15.
10. For one degree of freedom planer mechanism having links, which one of the following is the possible combination?
a) Four binary links and two ternary links
b) Four ternary links and two binary links
c) Three ternary links and three binary links
d) One ternary link and five binary links
Explanation: From Grubler’s criteria 1 = 3(l – 1) – 2j
or, j = 3/2l – 2 for six link
j = 3/2 x 6 – 2 = 7 1 ternary link = 2 binary link
a) j = 4 + 2 x 2 ≠ 7
b) j = 4 x 2 + 2 ≠ 7
c) j = 3 x 2 + 2 ≠ 7
d) j = 1 x 2 + 5 ≠ 7
the ans is d.