Question about rotational energy.

AI Thread Summary
To determine the order of increasing rotational energy for the five objects, the moment of inertia (I) must first be calculated for each object using the formula E = (1/2)Iw^2. The objects include a solid sphere, thin rod, solid cylinder, thin spherical shell, and thin cylindrical shell, each with specified dimensions and angular velocities. Since all objects have equal mass, the ranking of their rotational energies can be derived from their moments of inertia and angular velocities. The discussion emphasizes the importance of consulting a textbook for the specific moments of inertia for each shape. Ultimately, understanding these principles allows for the correct ranking of the objects based on their rotational energy.
physicsbro
Messages
10
Reaction score
0

Homework Statement


Five objects of equal mass are shown below together with the axis about which they are rotating. Select the objects in order of increasing rotational energy

Solid Sphere, about any diameter, with R = 3 m and ω=5 rad/s


Thin rod, about axis through center, perpendicular to the length with l = 8 m and ω=6 rad/s


Solid Cylinder, about cylinder axis with R = 3 m and ω=5 rad/s


Thin Spherical shell, about any diameter, with R = 2 m and ω=7 rad/s


Thin cylindrical shell, about cylinder axis with R = 1 m and ω=7 rad/s



Homework Equations



(1/2)Iw^2

The Attempt at a Solution



Most of these have no mass or moment of intertia included and I am not sure how to deal with that.
 
Physics news on Phys.org
You are supposed to calculate the moments of inertia first. Your textbook must have a table where these are listed. Note that all the masses are the same, therefore you can rank the energies because they will always be

E = (some number)*m
 
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top