PlacementPrepThe number of degrees of freedom of a four-bar mechanism is:
Solution
Gruebler: 3(4 − 1) − 2 × 4 = 1.
Answer: (B) 1
Technical · Mechanical Engineering
Theory of Machines MCQs for placement tests
20 technical questions of moderate difficulty, as asked in campus placement and company tests. Each has a short explanation.
Grashof's law for a four-bar linkage concerns:
Solution
If s + l ≤ p + q, at least one link can make a full rotation.
Answer: (D) Whether at least one link can rotate fully
A cam with a roller follower converts:
Solution
The cam profile drives the follower up and down.
Answer: (D) Rotary motion into reciprocating motion
The purpose of a flywheel is to:
Solution
It stores energy when supply exceeds demand and releases it later.
Answer: (D) Reduce speed fluctuations within a cycle
A governor controls:
Solution
It adjusts fuel supply to keep mean speed steady.
Answer: (B) The mean speed of an engine with changing load
Two gears have 20 and 60 teeth. If the smaller gear runs at 900 rpm, the larger runs at:
Solution
N₂ = N₁ × T₁/T₂ = 900 × 20/60 = 300 rpm.
Answer: (B) 300 rpm
Which gears are used to connect intersecting shafts?
Solution
Bevel gears transmit motion between intersecting shafts.
Answer: (C) Bevel gears
Worm gears are used when:
Solution
They give high reduction ratios but lower efficiency.
Answer: (B) A large speed reduction is needed between non-intersecting perpendicular shafts
The law of gearing requires that the common normal at the point of contact passes through:
Solution
This keeps the velocity ratio constant.
Answer: (A) The pitch point
Belt drives may slip because of:
Solution
Slip reduces the velocity ratio.
Answer: (C) Insufficient friction between belt and pulley
The ratio of tensions in a flat belt drive is:
Solution
T₁/T₂ = eμθ, where θ is the angle of contact.
Answer: (A) eμθ
Resonance in a vibrating system occurs when:
Solution
Amplitude becomes very large at resonance.
Answer: (D) The forcing frequency equals the natural frequency
The natural frequency of a spring-mass system is:
Solution
ωn = √(k/m) rad/s.
Answer: (C) √(k/m)
Critical speed of a shaft is the speed at which:
Solution
It coincides with the natural frequency of transverse vibration.
Answer: (C) It whirls with very large deflection
A gyroscopic couple acts on a ship when it:
Solution
Changing the direction of a spinning rotor's axis creates a gyroscopic couple.
Answer: (B) Turns while its turbine rotor spins
Which mechanism is used in the steam engine to convert reciprocating motion into rotary motion?
Solution
The piston drives the crank through a connecting rod.
Answer: (C) Slider-crank mechanism
The velocity ratio of a simple gear train depends on:
Solution
Idler gears change direction but not the ratio.
Answer: (A) The number of teeth on the first and last gears only
Balancing of rotating masses is done to:
Solution
Unbalanced masses cause centrifugal forces.
Answer: (A) Reduce vibration and bearing loads
A clutch is used to:
Solution
It lets the engine run while the wheels are stopped.
Answer: (C) Connect and disconnect a driving and driven shaft
Which brake is commonly used in modern cars for front wheels?
Solution
Disc brakes give strong, fade-resistant braking.
Answer: (A) Disc brake
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