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Physics -- Circular, Rotational and Simple Harmonic Motions
21.
When a ceiling fan is switched on, it makes 10 rotations in the first 3 seconds. How many rotations will it make in the next
3 seconds? (Assume uniform angular acceleration.)
- A.10
- B.20
- C.30
- D.40
- Answer
- Report
Answer : [C]
22.
When a ceiling fan is switched off, its angular velocity falls to
half while it makes 36 rotations. How many more rotations will it
make before coming to rest? (Assume uniform angular
retardation.)
- A.36
- B.24
- C.18
- D.12
- Answer
- Report
Answer : [D]
23.
A flywheel rotates about an axis. Due to friction at the axis, it experiences an angular retardation proportional to its angular velocity. If its angular velocity falls to half while it makes n rotations, how many more rotations will it make before coming
to rest?
- A.2n
- B.n
- C.n/2
- D.n/3
- Answer
- Report
Answer : [B]
24.
A flywheel rotating about an axis experiences an angular retardation proportional to the angle through which it rotates. If its rotational kinetic energy gets reduced by ∆E while it rotates through an angle θ then
- A.∆E ∝ θ2
- B.∆E ∝ √θ
- C.∆E ∝ θ
- D.∆E ∝ θ3/2
- Answer
- Report
Answer : [A]
25.
Two identical rods are joined to form an ‘X’. The smaller angle between the rods is θ. The moment of inertia of the system about an axis passing through the point of intersection of the rods and perpendicular to their plane is
- A.∝θ
- B.∝sin2θ
- C.∝cos2θ
- D.independent of θ
- Answer
- Report
Answer : [D]
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