Tagged Questions
2
votes
1answer
228 views
Why is an electric motor more efficient at higher loads?
My question is driven by the plot below. We see that acceptable operating range of a motor is between 50-100% of the rated load. Below 40% or so the efficiency of the motor drops off dramatically.
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1
vote
2answers
78 views
Ice skater increase of energy
This may be a very basic question but I am not seeing how it works.
Consider the standard example of an ice skate rotating about his/her center of mass and pulling in his/her arms. The torque is zero ...
0
votes
1answer
291 views
Finding Rotational Kinetic Energy Of A Clock
The problem I am working on is:
"Big Ben, the Parliament tower clock in London, has an hour hand 2.70 m long with a mass of 300 kg, and a minute hand 4.20 m long with a mass of 100 kg (see figure ...
8
votes
2answers
614 views
Hamiltonian is conserved, but is not the total mechanical energy
I wondering about the interpretation for the energy difference between the Hamiltonian and the total mechanical energy for systems where the Hamiltonian is conserved, but it is not equal to the total ...
0
votes
2answers
1k views
Rotational kinetic energy during vertical circular motion of a particle
Why is it not necessary to take into account rotational kinetic energy when using the Law of Conservation of Mechanical Energy to solve vertical circular motion problems? After all, the particle is ...
1
vote
4answers
612 views
17 Joules of Energy From a Mouse Trap
Do you think it would be possible to get 17 joules out of a standard size mouse trap. By my math, it is a torsion coefficient of 3.45 or so out of the spring.
1
vote
0answers
237 views
How equivalent are heat energy and work energy in connection with a spinning flywheel?
Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper.
Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
2
votes
1answer
185 views
What happens to a rotating rod that breaks in two?
I know that the approximation for the moment of inertia of an infinitely thin rod of mass $m$ and length $L$ spinning around an axis perpendicular to its own axis at its center is $\frac{mL^2}{3}$:
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2
votes
1answer
180 views
What “I” should use in Rotational Energy formula $(I \omega^2)/2$
$\text{Rotational Energy} = \frac{1}{2} I \omega^2$. What $I$ should be used?
$I$ as a inertia tensor matrix = stepRotation * inverse moment of inertia * inverse stepRotation;
Or I as moment of ...
5
votes
1answer
280 views
Does rotational energy have effect on gravity/metric?
Intuitively, if energy can be stored in rotational motion, it has to obey $E=mc^2$.
Does rotation of typical stellar-sized objects - BHs, pulsars, binaries - have measurable effect on their overall ...
