# If a 1000kg Mass resting on a friction free airbed....

1. Mar 5, 2017

### Fizzics

Question: If a 1000kg Mass resting on a friction free airbed is accelerated from zero to 1 Metre per second by a drive motor, then the motor is disconnected, how much electrical braking energy could be recovered from the moving mass in percentage terms using modern technology. Thank you in advance for your considered replies which should be very helpful to me.

2. Mar 5, 2017

### .Scott

If the mass is a magnet traveling through the coil of a linear motor, then the efficiency should be comparable to a power transformer - in the commercial sector, about 95 to 98.5%.
It depends on how "off-the-shelf" you require. If you want to use super-conductors, you could get higher efficiencies.

3. Mar 5, 2017

### Fizzics

Hi Scott,
I'm talking about a non magnetic mass accelerating then deaccelerating in a linear fashion oscillating backwards and forwards, I was also wondering whether it is actually possible to have a 1000kg magnet working in the way you have suggested?

4. Mar 5, 2017

### .Scott

Am I allowed to attach something to it? If I do nothing, how long will it stay on the track? Is it also subject to air resistance?
If it's non-magnetic, I will need to "touch" it in some other way. For example,attaching it to a magnet or placing it onto a trolley.
What are your rules?

Can I arrange an elastic collision between the 1Mg mass and another 1Mg mass that is magnetic?

5. Mar 5, 2017

### Fizzics

Hi Scott
Thanks for your feedback it has been very helpful and food for thought, I hope to come back with a reply to your last question in the next couple of days.

6. Mar 6, 2017

### Baluncore

Why accelerate and decelerate if you do not need to? A big spring at each end of the track, or one mounted on the cart would be more economical.
If it was a railway I would advocate raising the ends of the track. If you needed a longer time at the ends a flat "landing" could be provided.