These 40 MCQs cover a range of topics in the Theory of Machines, including mechanisms, gear trains, vibrations, and governor systems. They are designed to test both basic understanding and more advanced concepts in the field.
1. Which of the following is a scalar quantity in mechanics?
Answer:
Explanation:
Energy is a scalar quantity as it does not have a direction, unlike vector quantities like force, velocity, and displacement.
2. The Grashof's law states that for a four-bar linkage to be movable, the sum of the shortest and longest link lengths should be _______ the sum of the other two links.
Answer:
Explanation:
Grashof's law for a four-bar linkage mechanism states that the sum of the shortest and longest links should be less than or equal to the sum of the other two link lengths.
3. What is the mechanical advantage of an ideal lever?
Answer:
Explanation:
The mechanical advantage of a lever is the ratio of the distance from the fulcrum to the load and the distance from the fulcrum to the effort.
4. In a cam mechanism, the follower moves in a direction perpendicular to the cam axis in _______ cam.
Answer:
Explanation:
In a radial cam, the follower moves in a direction perpendicular to the cam axis.
5. What type of motion is imparted by a crank and slotted lever quick return motion mechanism?
Answer:
Explanation:
A crank and slotted lever mechanism imparts reciprocating motion.
6. In a gear train, if the number of teeth on the driver and the driven gears are equal, then the gear train is said to be:
Answer:
Explanation:
If the number of teeth on both the driver and the driven gears are equal, the gear train is said to be direct, maintaining the same speed.
7. Which of the following is not a type of rolling contact bearing?
Answer:
Explanation:
Bush bearings are plain bearings and do not come under rolling contact bearings.
8. A flywheel is used in machines to:
Answer:
Explanation:
A flywheel stores rotational energy and is used to maintain a constant angular velocity by storing or releasing energy.
9. What is the purpose of a governor in engines?
Answer:
Explanation:
A governor is used to regulate the mean speed of an engine when there are variations in the load.
10. The ratio of the driving force used in a belt drive to the tight side tension is known as:
Answer:
Explanation:
The slip ratio in a belt drive system is the ratio of the driving force to the tight side tension of the belt.
11. In a differential gear of an automobile, the number of teeth on the crown gear and the pinion are 40 and 10 respectively. What is the gear ratio?
Answer:
Explanation:
Gear ratio is the ratio of the number of teeth on the driven gear (crown gear) to the driver gear (pinion). Thus, it is 40/10 = 4.
12. What is the natural frequency of a mass-spring system with a mass of 2 kg and a spring stiffness of 100 N/m?
Answer:
Explanation:
The natural frequency \( \omega_n = \sqrt{\frac{k}{m}} \), where k is the spring stiffness and m is the mass. Substituting the given values, \( \omega_n = \sqrt{\frac{100}{2}} = 5 \) rad/s.
13. Which type of gear is used for non-intersecting perpendicular shafts?
Answer:
Explanation:
Worm gears are used to transmit power between non-intersecting perpendicular shafts.
14. The process of adjusting the axial position of a gear on a shaft for meshing with another gear is known as:
Answer:
Explanation:
Gear alignment is the process of adjusting the axial position of a gear for proper meshing.
15. The Coriolis component of acceleration is encountered in which of the following mechanisms?
Answer:
Explanation:
The Coriolis component of acceleration is significant in the slider-crank mechanism due to the sliding motion of the slider.
16. What does the term 'kinematic pair' mean in the context of Theory of Machines?
Answer:
Explanation:
A kinematic pair refers to two or more machine elements that have motion relative to each other.
17. What is the pitch circle diameter in gears?
Answer:
Explanation:
Pitch circle diameter is an imaginary circle in gears which is used to calculate gear size and meshing properties.
18. What kind of joint is formed when two links in a mechanism are in contact over the surface?
Answer:
Explanation:
A sliding pair is formed when two links are in contact over a surface allowing sliding motion.
19. A mechanism in which one link is fixed is known as:
Answer:
Explanation:
A mechanism is a combination of rigid bodies where one body is fixed, and the others move relative to it.
20. The phenomenon where the input and output shafts of a gearbox rotate in opposite directions is known as:
Answer:
Explanation:
Inversion in a gearbox refers to the scenario where the input and output shafts rotate in opposite directions.
21. The effort required to overcome friction in a screw jack is directly proportional to:
Answer:
Explanation:
The effort in a screw jack is directly proportional to the load on the screw and the coefficient of friction.
22. A centrifugal clutch is primarily used in:
Answer:
Explanation:
A centrifugal clutch is often used in automatic transmissions for engaging the drive automatically.
23. The law of gearing states that for constant velocity ratio, the common normal at the point of contact of two gear teeth must always pass through:
Answer:
Explanation:
According to the law of gearing, the common normal at the contact point of two gear teeth must pass through the pitch point for a constant velocity ratio.
24. In a four-bar chain, if the shortest link is adjacent to the longest link, the chain is known as:
Answer:
Explanation:
In a crank-rocker mechanism, the shortest link (crank) is adjacent to the longest link.
25. What is the function of a universal joint in a vehicle?
Answer:
Explanation:
A universal joint in a vehicle is used to allow for variations in the alignment of the drive shaft, particularly in rear-wheel-drive vehicles.
26. In a reciprocating steam engine, the link that connects the piston to the crankshaft is known as:
Answer:
Explanation:
The connecting rod in a reciprocating steam engine connects the piston to the crankshaft, transferring the reciprocating motion of the piston into rotary motion of the crankshaft.
27. Which of the following is not a lower pair mechanism?
Answer:
Explanation:
A gear pair is a higher pair mechanism as the contact between the gear teeth is point or line contact. Lower pairs like revolute, prismatic, and helical pairs have surface contact.
28. In vibrations, damping is used to:
Answer:
Explanation:
Damping is used in vibration systems to reduce or damp out the amplitude of oscillations.
29. The angle between the tangent to the cam profile and the direction of the follower motion is known as:
Answer:
Explanation:
The pressure angle in a cam mechanism is the angle between the tangent to the cam profile and the direction of follower motion. It is critical in cam design for smooth operation.
30. What is the primary function of a fusee in a clock mechanism?
Answer:
Explanation:
A fusee in a clock mechanism is used to equalize the force of the mainspring to ensure uniform movement and accurate timekeeping.
31. The phenomenon of a body vibrating with decreasing amplitude under the action of external forces is known as:
Answer:
Explanation:
Damped vibration refers to the vibration of a body under the action of external forces that gradually reduce its amplitude over time.
32. Which mechanism converts rotary motion into oscillatory motion?
Answer:
Explanation:
The Scotch Yoke mechanism converts rotary motion of a crank into oscillatory motion of a slider.
33. In a belt drive, if the belt moves towards the slack side, the alignment of the pulleys should be adjusted in which direction?
Answer:
Explanation:
If the belt moves towards the slack side, the pulleys should be adjusted towards the tight side to correct the alignment.
34. A mechanism with four links is known as:
Answer:
Explanation:
A mechanism with four links is commonly referred to as a four-bar mechanism, which is the simplest movable closed-chain linkage.
35. What is the purpose of a flyball in a centrifugal governor?
Answer:
Explanation:
In a centrifugal governor, flyballs are used to regulate the speed of the engine by adjusting the fuel supply based on the centrifugal force generated by the rotating balls.
36. The point on a gear tooth where the pressure angle is measured is called the:
Answer:
Explanation:
The pressure angle on a gear tooth is measured at the pitch point, which is a point on the pitch circle of the gear.
37. In a hydraulic system, what is the function of a relief valve?
Answer:
Explanation:
A relief valve in a hydraulic system is used to regulate or limit the maximum pressure in the system to prevent damage or failure.
38. A gear train with a large speed reduction in a compact space can be achieved by using:
Answer:
Explanation:
Planetary gear trains are capable of achieving large speed reductions in a compact space due to their unique arrangement of central and orbiting gears.
39. The acceleration of a point on a link in planar motion can be determined using:
Answer:
Explanation:
Klein's construction is a graphical method used to determine the acceleration of a point on a link in planar motion.
40. In a slider-crank mechanism, the length of the crank and the connecting rod are 100 mm and 400 mm, respectively. What is the transmission angle when the crank is at 30 degrees from the inner dead center?
Answer:
Explanation:
The transmission angle in a slider-crank mechanism is the angle between the connecting rod and a line perpendicular to the slider motion. It can be calculated using the geometric relations in the mechanism.