Two disks are mounted (like a merry-go-round) on low-friction bearings on the sa

Question

Two disks are mounted (like a merry-go-round) on low-friction bearings on the same axle and can be brought together so that they couple and rotate as one unit. The first disk, with rotational inertia 3.0 kg m^2 about its central axis, is set spinning counterclockwise at 500 rev/min. The second disk, with rotational inertia 5.6 kg m^2 about its central axis, is set spinning counterclockwise at 800 rev/min. They then couple together. What is their angular speed after coupling? rev/min If instead the second disk is set spinning clockwise at 800 rev/min, what is the angular velocity after coupling? (Include the sign. Take counterclockwise to be positive.)

Explanation / Answer

(a) Conservation of rotational momentum
3 kg·m2 ( 500 rev/min. ) + 5.6 kg·m2( 800 rev/min.) = (3 kg·m2 + 5.6 kg·m2)

= _____695.35___rev/min

(b) If instead the second disk is set spinning at 800 rev/min in the direction opposite the first disk's rotation, what is their rotational speed and direction after coupling?
3 kg·m2 ( 500 rev/min. ) - 5.6 kg·m2( 800 rev/min.) = (3 kg·m2 + 5.6 kg·m2)

=_____-346.5____rev/min opposite the first disk's rotation

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.