Two disks of identical mass but different radii ( r and2 r ) are spinning on fri

Question

Two disks of identical mass but different radii (r and2r) are spinning on frictionless bearings at the sameangular speed 0, but in oppositedirections. The two disks are brought slowly together. Theresulting frictional force between the surfaces eventually bringsthem to a common angular velocity.
(a) What is the magnitude of that final angular velocity in termsof 0? (Use the following variables asnecessary: omega_0 for 0.)
1

(b) What is the change in rotational kinetic energy of the system?(Take K as the initial kinetic energy.)
2

Explain.
3

(a) What is the magnitude of that final angular velocity in termsof 0? (Use the following variables asnecessary: omega_0 for 0.)
1

(b) What is the change in rotational kinetic energy of the system?(Take K as the initial kinetic energy.)
2

Explain.
3

Explanation / Answer

moment of inertia r disk : I1=1/2*m*r2 2r disk I2=1/2*m*4*r2=2*m*r2 conservation of momentum -I1*0+I2*0=(I1+I2)* =>=3/5*0 (b) the change in rotational kinetic energy of thesystem K-K2=1/2*(I1+I2)*02-1/2*(I1+I2)*2 =4/5*m*r2*02 ,reduced if count on direction : change = -4/5*m*r2*02 if count on direction : change = -4/5*m*r2*02

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

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