Motor which operate solely on magnet and gravity?

205
0
I received an assignment from my professor which sounds like follow:

"Suggest a motor which operates only on magnets and gravitational force."

While I did make a search online and found some model which seems to work, I am sill a little skeptical (There are videos online, but none of them are authentic). Are there any design which full fills such requirement, and has been verified? I was told that such machine would not violate the 2nd Law of Thermodynamics because the magnet itself is the energy source. Can anyone verified / debunk this?

Thanks in advanced.
 

mgb_phys

Science Advisor
Homework Helper
7,660
11
Without any external energy input - it's going to be tricky.
Otherwise it's quite easy.
1, Attach plastic paddle wheel to electric motor.
2, Stand above it
3, Drop magnets onto paddle wheel.
4, Motor turns - generates electricity
 

Bobbywhy

Gold Member
1,709
45
You may try putting a permanent magnet on a Focault pendulum.
As the pendulum precesses the magnetic interacts with the earth's magnetic field and adds kinetic energy!
 

Ivan Seeking

Staff Emeritus
Science Advisor
Gold Member
6,781
169
It not only violates the second law, it also violates Ivan's law. :biggrin:

Perpetual motion/free energy discussions are banned because it [such a motor] would violate the second law.

There is a small amount of energy stored in the field of a magnet, but only a very little bit. And there is no way to switch it on and off as we would do for a motor using electromagnets, brushes, and a rotor.
 

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