# Theory of Machines - GATE practice papers - Mechanical

Here, you can read Theory of Machines multiple choice questions and answers with explanation.

1)   Which of the following statements is wrong?

(1) A statically balanced rotor is always dynamically balanced
(2) A dynamically balanced rotor is always statically balanced (Marks: 02)

- Published on 19 Oct 15

a. Only (1)
b. Only (2)
c. both (1) and (2)
d. both are correct
 Answer  Explanation ANSWER: Only (1) Explanation: When rotor is dynamically balanced then it is always statically balanced. But when rotor is statically balanced then it may or may not be dynamically balanced.

2)   The punching rate of a punching press is 20 holes per minute. It is required to punch a hole of diameter 50 mm on a plate of 20 mm thickness. Press requires 10 N-m of energy per mm2 of sheared area. Calculate the energy required for punching work per second. (Marks: 02)
- Published on 19 Oct 15

a. 628318.2 Nm/s
b. 10471.97 Nm/s
c. 31416 Nm/s
d. none of the above
 Answer  Explanation ANSWER: 10471.97 Nm/s Explanation: d =50 mmt = 20 mmNumber of holes = 20 holes per minuteEnergy required = 10 N-m/mm 2Sheared area per hole = πdt= π × 50 × 20= 3141.6 mm2Energy required to punch one hole = 3141.6 × 10= 31416 N-mand the energy required for punching work per second= energy required per hole × number of holes per second= 31416 × (20/60)= 10471.97 Nm/s

3)   How is the kinematic pair formed?(Marks: 01)
- Published on 19 Oct 15

a. when two kinematic links of a machine are in contact with each other and relative motion between them is not completely constrained
b. when two kinematic links of a machine are in contact with each other and relative motion between them is completely constrained
c. both a. and b.
d. none of the above
 Answer  Explanation ANSWER: when two kinematic links of a machine are in contact with each other and relative motion between them is completely constrained Explanation: When two kinematic links or elements are in contact with each other, they are said to form a pair and if the relative motion between them is completely constrained, the pair is called as kinematic pair.

4)   The part of machine which is resistant and undergoes relative motion is called as __________(Marks: 01)
- Published on 19 Oct 15