A student sitting on a frictionless rotating stool has rotational inertia 0.90kg

Question

A student sitting on a frictionless rotating stool has rotational inertia 0.90kgcdot m^2 about a vertical axis through her center of mass when her arms are tight to her chest. The stool rotates at 6.80rad/s and has negligible mass. The student extends her arms until her hands, each holding a 5.0kg mass, are 0.79m from the rotation axis. Part A: Ignoring her arm mass, what's her new rotational velocity? Express your answer to two significant figures and include the appropriate units. The answer to this part is .86 rad/s Part B: Repeat if each arm is modeled as a 0.79m long uniform rod of mass of 4.8kg and her total body mass is 60kg . Express your answer to two significant figures and include the appropriate units. Please tell me the exact answer for the second part.

Explanation / Answer

I1W1 = (I1+ I2)W2 I2 = 0.5 MR^2 0.9 X 6.8 = ( 0.9 + 6.24 )W2 W2 = 0.857 rad /s = 0.86 rad /s now if arms are modelled as , rods, then I = 1/3 ML^2 I1W1 =( I1+I2)W2 I2 = 2 X 0.33 X 4.8 X 0.79X0.79 = 0.1977

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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