Rotational Inertia of compass needle

AI Thread Summary
The discussion centers on calculating the rotational inertia of a compass needle in a uniform magnetic field, given its oscillation frequency of 5 Hz and the work required to twist it 180º. Participants are encouraged to consider relevant equations related to oscillation frequency and the energy of a magnetic dipole. The initial inquiry highlights a lack of understanding on how to approach the problem, prompting requests for guidance on applicable formulas. Key concepts include the relationship between frequency, work, and rotational inertia in the context of magnetic fields. The conversation aims to clarify these principles to solve the problem effectively.
olyviab
Messages
10
Reaction score
0

Homework Statement



A small compass needle is situated in a uniform magnetic field. When displaced from its stable equilibrium position through a small angle and then released, it oscillates with a frequency of 5 Hz. A millijoule of work is needed to twist the compass needle round through 180º, so that its magnetic moment is in the opposite direction to the magnetic field. What is the rotational inertia of the needle?


2. The attempt at a solution

I don't understand how to start this problem any help would be great.
 
Physics news on Phys.org
What equations have you learned that involve the frequency of oscillation? What about the work (or energy) of a dipole in a uniform magnetic field?
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

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...
View full post »

Similar threads

Distance of compass to wire based on magnetic field strength
Replies
3
Views
2K
Moment of Inertia Compass Needle
Replies
18
Views
4K
Calculate the intensity of the Earth's magnetic field
Replies
2
Views
2K
B Why does my LC circuit not oscillate its energy between Electric & Magnetic fields?
4
Replies
152
Views
6K
Compass needle, magnetic field and current
Replies
8
Views
2K
I Stern-Gerlach experiment with a classical object
Replies
2
Views
1K
Oscillations in a magnetic field
Replies
1
Views
3K
Why can we use this approximation in rotational work-kinetic energy theorem for small displacements?
Replies
7
Views
1K
How Does Adding Masses Affect the Angular Velocity of a Rotating Cylinder?
Replies
12
Views
3K
Wire & Compass Homework: Effects of Distance & Series Batteries
Replies
1
Views
22K

Hot Threads

Recent Insights

Back
Top