A massless frame in the shape of a square with 2-m sides has a 1-kg ball at each

Question

A massless frame in the shape of a square with 2-m sides has a 1-kg ball at each corner. The frame is rotating at a rotational speed of 5 rad/s about an axis through the corner marked O and perpendicular to the plane of the paper. How much work (in joules) would have to be done to bring the system of frame with masses to rest? A) 200 B) 240 C) 300 D) 360 E) None of these 20. A uniform disk (I = 1/2 MR2) of radius 1.2 m and mass 0.60 kg is rotating at 25 rad/s around an axis that passes through its center and is perpendicular to the disk. A rod makes contact with the rotating disk with a force of 4.5 N at a point 0.75 m from the axis of rotation as shown. The coefficient of kinetic friction for the two materials in contact is 0.20. Through about how many radians will the disk turn in the next 3.0 seconds? A) 32 B)45 C) 54 D)68 E) None of these

Explanation / Answer

1-Any rotating frame having moment of inertia I and angular velocity w,have rotational energy of 0.5*I*w2 .if we want to stop the frame then we have to supply this much energy in the form of the work done-

I = 1*22 + 1*(21.5)2 + 1*22 +1*0

I = 16 kg-m2

rotational energy = 0.5*I*w2

E =0.5*16*25

E =200 jule

so this 200 jule work done will be required to bring the system in rest.

2- This force will apply friction which will generate torque about of centre of mass and cause angular de-acceleration in the disk

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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