250+ TOP MCQs on Effect of Gyroscopic Couple on a Disc Fixed Rigidly at a Certain Angle to a Rotating Shaft and Answers

Machine Dynamics Interview Questions on “Effect of Gyroscopic Couple on a Disc Fixed Rigidly at a Certain Angle to a Rotating Shaft”.

1. In the figure given below, the moment of inertia about polar axis OP is _______
a) mr²/2
b) mr²
c) 2mr²
d) 4mr²

Answer: a
Clarification: In the figure given above, if m is the mass of the disk and r is the radius, then the moment of inertia about the axis OP is given by mr²/2.

2. When seen from the top, the gyroscopic couple acting on the disc will act in the clockwise direction.
a) True
b) False

Answer: b
Clarification: When seen from the top, the gyroscopic couple acting on the disc will act in the anti-clockwise direction.

3. In the figure given below, the moment of inertia about diametral axis is _______
a) m(l²/12 + r²/4)
b) m(l²/6 + r²/4)
c) m(l²/12 + r²/2)
d) m(l²/12 + r²)

Answer: a
Clarification: If m is the mass, l is the length and r is the radius of the disc, then the moment of inertia about the diametral axis is given by m(l²/12 + r²/4).

4. If the length of the disc is negligible, then what will be the moment of inertia about the diametral axis?
a) mr²/4
b) mr²
c) mr²/2
d) 2mr²

Answer: a
Clarification: If m is the mass, l is the length and r is the radius of the disc, then the moment of inertia about the diametral axis is given by m (l²/12 + r²/4), if l is negligible then the expression becomes
mr²/4.

5. If the length and radius of the disc is same them moment of inertia is more about which axis?
a) Polar
b) Diametral
c) Shaft
d) Center

Answer: a
Clarification: If the length and radius are same then the moment of inertia will be more about the polar axis. Mr²/2 as compared to mr²/3.

6. From the following data calculate the gyroscopic couple on the bearing in N-m.
Mass of disc = 30 Kg, diameter = 60 cm
Rotation speed = 1200 rpm
Angle between disc and a plane 90 degree to the axis of shaft = 1°
a) 180
b) 186
c) 190
d) 196

Answer: b
Clarification: ω = 125.7 rad/s
Couple acting on the bearings
= mω²r²/8 sin2θ
substituting the values we get
C = 186 N-m.

7. If the rotation speed of the disc is increased to 2 times and the mass is reduced to half, overall the Couple acting on bearings will increase.
a) True
b) False

Answer: a
Clarification: If the rotation speed of the disc is increased to 2 times and the mass is reduced to half, overall the Couple acting on bearings will increase as couple on bearing depends on the relation
mω²r²/8 sin2θ, hence it will increase by two times.