Rotational Equilibrium and Dynamics -

AI Thread Summary
The discussion centers on calculating the initial and final rotational kinetic energy of a skater who changes his moment of inertia while spinning. The formula for rotational kinetic energy, KE = 1/2·I·ω², is confirmed as correct. The initial moment of inertia is given as 41 kg·m², and the final moment of inertia is 36 kg·m², with the angular speed remaining at 12.0 rad/s. Participants emphasize using the conservation of angular momentum to find the kinetic energy values. The conversation concludes with clarification on using the provided inertia values for calculations.
raconteur
Messages
2
Reaction score
0
Rotational Equilibrium and Dynamics - :)

I'm totally stumped!
---------------------
A skater spins with an angular speed of 12.0 rad/s with his arms outstretched. He lowers his arms, decreasing his moment of inertia from 41 kg·m² to 36 kg·m²

Calculate his initial and final rotational kinetic energy.
----------------------
Is the formula KE=1/2·I·ω² ?
ω=angular speed.. so ω=12.0 rad/s
so then how would i get I (inertia) ?
and how would i find out initial and final ?
---------------------
i just need some help
 
Last edited:
Physics news on Phys.org
s the formula KE=1/2·I·ω² ?
yes
so then how would i get I (inertia) ?
its given. read the question

and how would i find out initial and final ?
Use conservation of Angular momentum.
 
^^^
hmm, i think i get it

so.. i use (plug in) 41 kg·m² to get my initial and 36 kg·m² to my my final?
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

What's the source of increase in rotational energy of carousel?
Replies
9
Views
2K
Angular Momentum Problem: Mouse walking on a rotating turntable
Replies
5
Views
1K
Rotational Motion and moments of inertia
Replies
9
Views
2K
Rotating simple harmonic oscillator
Replies
11
Views
1K
Angular momentum and a summersault problem
Replies
19
Views
2K
Avg Power in a Rotational Energy/Work Problem
Replies
6
Views
1K
Masses Moving Radially on a Rotating Disk
Replies
8
Views
2K
Help with Angular Velocity True-False Question
Replies
12
Views
1K
Why can we use this approximation in rotational work-kinetic energy theorem for small displacements?
Replies
7
Views
1K
What is the net acceleration of the coin on a rotating disk?
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top