Motor which operate solely on magnet and gravity?

  • Thread starter Harmony
  • Start date
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.


Science Advisor
Homework Helper
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


Gold Member
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
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.

Want to reply to this thread?

"Motor which operate solely on magnet and gravity?" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Top Threads