Rotation problem: which would stop first?

  • Thread starter Thread starter Misako
  • Start date Start date
  • Tags Tags
    Rotation
Click For Summary
SUMMARY

The discussion centers on a physics problem involving two razor fans of different sizes and their stopping times. The larger fan is expected to stop later than the smaller fan due to differences in angular momentum and energy dissipation. Key concepts include angular velocity and energy proportionality related to the radius of the fans. The participants suggest considering torque and energy loss rates to derive a solution.

PREREQUISITES
  • Understanding of angular velocity and its calculation
  • Basic knowledge of torque and its effects on rotational motion
  • Familiarity with energy conservation principles in physics
  • Ability to analyze proportional relationships in physical equations
NEXT STEPS
  • Study the relationship between torque and angular acceleration in rotational dynamics
  • Learn about the conservation of angular momentum and its implications
  • Explore energy loss mechanisms in rotating systems
  • Investigate how radius affects the moment of inertia and stopping time
USEFUL FOR

Students in physics, particularly those in middle school or early high school, who are learning about rotational motion and energy concepts. This discussion is also beneficial for educators looking for practical examples to explain these principles.

Misako
Messages
1
Reaction score
0
Hey! I'm new here in PF and is wanting to solve this teeny bitsy problem about rotation. I'm at 9th grade and is a newbie at physics. :p

Homework Statement



Two razor fans, one larger and one smaller, were turned on at the same time and turned off at the same time.

Question: which fan would stop first? the larger one or the smaller one?


Homework Equations



I'm thinking of: angular velocity = delta s/ r x delta t

The Attempt at a Solution



I need to prove the answer by using an equation. So the equation must include probably a radius(for the smaller and larger blade) and the time. Problem is, i can't seem to find that and is stumped. But for me, I really think the smaller fan would stop first.

Halp? =(
 
Physics news on Phys.org
Welcome to PF.

Has torque been discussed in your class?
 
Welcome to PF!

Hi Misako! Welcome to PF! :smile:

hmm … that seems rather difficult for 9th grade :redface: …

let's assume they're turning at the same angular rate …

what is the initial energy proportional to, r r2 or r3?

and what is the rate of energy loss proportional to? :smile:
 

Similar threads

Angular Momentum Problem: Mouse walking on a rotating turntable
  • · Replies 5 ·
Replies
5
Views
2K
Intuition on the direction of friction in a rotational dynamics problem
  • · Replies 13 ·
Replies
13
Views
2K
Circular Motion Application Question
  • · Replies 1 ·
Replies
1
Views
1K
Understanding work in translation and rotation of a magnetic dipole
  • · Replies 1 ·
Replies
1
Views
2K
Center of mass and momentum- A question about systems
  • · Replies 25 ·
Replies
25
Views
2K
Different diameter rotational inertia
  • · Replies 7 ·
Replies
7
Views
2K
Help calculating the uncertainty in the Sun's rotational speed
  • · Replies 4 ·
Replies
4
Views
2K
Rotational motion problem, half solved, can't figure out other half.
  • · Replies 1 ·
Replies
1
Views
7K
Find Distance d for Impulse on Stick to Rotate Once
  • · Replies 13 ·
Replies
13
Views
2K
Rotational Motion - 2 Disc System
  • · Replies 2 ·
Replies
2
Views
2K