1. Inversion of a kinematic chain relative to some other links is a property of the chain and is not that of the mechanism.
a) True
b) False
Explanation: In a kinematic inversion relative motion does not change but absolute motion change drastically.
2. In a shaping operation, the average cutting speed is ( Stroke length S, Number of strokes per minute N, Quick return ratio R)
a) NSR
b) NSR/2
c) NS(1 + R)
d) NS(1 + R)/2
Explanation: Time for forward stroke + Tf
Time for return stroke = Tr
R = Tr/Tf
Therefore, time for only one cutting stroke(T) = 1/N x Tf/(Tf + Tr)
Average cutting speed = S/T = SN(Tf + Tr)/Tf = SN(1 + R).
3. In a kinematic inversion, the relative motions between links of the mechanism change as different links are made the frame by turns.
a) True
b) False
Explanation: Through the process of inversion the relative motions between the various links is not changed in any manner but their absolute motions may be changed drastically.
4. An elliptical trammel is a mechanism with three prismatic pairs and one revolute pair.
a) True
b) False
Explanation: Elliptical trammels have two sliding pairs and two turning pairs. It is an instrument used for drawing ellipse.
5.In a crank and slotted lever quick-return motion, the distance between the fixed centres is 150 mm and the length of the driving crank is 75mm. the ratio of the time taken on the cutting and return strokes is
a) 1.5
b) 2.0
c) 2.2
d) 2.93
Explanation: OA = 150mm
AB = 75 mm
sin (90 – α/2) = AB/OA
cosα/2 = 1/2
therefore, α = 1200
β = 3600 – 1200 = 2400
Quick return ratio = β/α = 240/120 = 2.
6. A helical coil spring of stiffness k is cut to two equal halves and then these are connected in parallel to support a vibrating mass m. The angular frequency of vibration, ωn is
a) √k/m
b) √2k/m
c) √4k/m
d) √k/4m
Explanation: stiffness ∞ 1/length
keq = 2k + 2k = 4k
ω = √4k/m.
7. Consider the following statements:
In a slider-crank mechanism, the slider is at its dead centre position when the
(i) slider velocity is zero
(ii) slider velocity is maximum
(iii) slider acceleration is zero
(iv) slider acceleration is maximum
Which of the above statements are correct?
a) 1 and 4
b) 1 and 3
c) 2 and 3
d) 2 and 4
Explanation: At dead centre velocity is zero, because instantaneous acceleration is maximum.
8. Which one of the following mechanisms is an inversion of double slider-crank chain?
a) Elliptic trammels
b) Beam engine
c) Oscillating cylinder engine
d) Coupling rod of a locomotive
Explanation: Elliptic trammels are inversion of double slider crank chain.
9. The number of instantaneous centres of rotation for a 10-link kinematic chain is
a) 36
b) 90
c) 120
d) 45
Explanation: Instantaneous centre = n(n – 1)/2 = 45
10. A slider moves with uniform velocity on a revolving link of length r with angular velocity ω. The Coriolis acceleration component of a point on the slider relative to a coincident point on the link is equal to
a) ω parallel to the link
b) 2ω perpendicular to the link
c) ω perpendicular to the link
d) 2ω parallel to the link
Explanation: coriolis components of acceleration for slider is perpendicular to the link.