# Power output from a falling masss over a time period

## Main Question or Discussion Point

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i need a falling mass over time /joules per kilo over 1hr time
also need to know how to figure gearing to maintain fall over time in regards to a set resistance such as a 5 kw alternator

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## Answers and Replies

anorlunda
Mentor
Welcome to PF. This is the New Member Introduction section. It is not for questions.

Your question might fit best at

https://www.physicsforums.com/forums/general-engineering.113/

But before posting there, I suggest that you specify the question better. The first question about joules, is that for a free-falling mass? The second question is definitely not free-fall.

Regarding the second question, what are you trying to design, a gravity lighting system perhaps? We can give better answers if we know more. Without knowing anything, I say for the second question to make the fall last longer, lift it higher. I don't think that is what you want.

Welcome to PF. This is the New Member Introduction section. It is not for questions.

Your question might fit best at

https://www.physicsforums.com/forums/general-engineering.113/

But before posting there, I suggest that you specify the question better. The first question about joules, is that for a free-falling mass? The second question is definitely not free-fall.

Regarding the second question, what are you trying to design, a gravity lighting system perhaps? We can give better answers if we know more. Without knowing anything, I say for the second question to make the fall last longer, lift it higher. I don't think that is what you want.
Consider both questions are related
A gravity light is the best similar concept I can think of
I just need a plug and play formula for a very large mass and gearing for it

Also
I wasn't sure what response was needed in intro
Lol

anorlunda
Mentor
10 ft
1,000,000 kilos
I would like to use 10 ft per hr as a guide and insert time and value according to given circumstance.

anorlunda
Mentor
1,000,000 kilos is about this size

How about 1 million liters of water? That's a lot more practical. You pump the water uphill, then make electricity as it comes down. The round trip efficiency is about 80%. We call it pumped hydro power. For that, 5 kw is pretty small.

Read more about it:
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

russ_watters
Mentor
10 ft
1,000,000 kilos
I would like to use 10 ft per hr as a guide and insert time and value according to given circumstance.
10ft is 3m. w=fd or for gravitational potential energy w=mgh. Can you do the calculation?

1,000,000 kilos is about this size

View attachment 251933

How about 1 million liters of water? That's a lot more practical. You pump the water uphill, then make electricity as it comes down. The round trip efficiency is about 80%. We call it pumped hydro power. For that, 5 kw is pretty small.

Read more about it:
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
Lol
I understand what you are saying
But
I can't give you all the info w out a non discloser agreement
The numbers I am using are examples and are small compared to actual
As long as we keep derivitives of 10
I should be able to keep the math from getting out of hand
I need to be able to not only understand the joules /weight to watts/time ratio but add and subtract it according to need functionality and whatever other perogitives are needed
Also
I have 10 ft of fall w said weight
Displacing said amount of water over 1 hr
Can I have a formula to show power generated by said water using a micro turbo or even a large turbine if it's possible
The possibilities are unlimited if you have a big enough hammer

Last edited by a moderator:
10 ft
1,000,000 kilos
I would like to use 10 ft per hr as a guide and insert time and value according to given circumstance.the sheer mass means I have to use a controlled fall to use the energy

10ft is 3m. w=fd or for gravitational potential energy w=mgh. Can you do the calculation?
Watts = distance times gravity potential times height
Doesn't the controlled fall change the equation by reducing the energy potential

russ_watters
Mentor
Watts = distance times gravity potential times height
No it doesn't.
Doesn't the controlled fall change the equation by reducing the energy potential
At best I don't think that sentence means anything.

Can you just try the math I gave you please. And pay attention to the units.

1,000,000 kg
3 meters
g = 9.81 m/s/s
29,430,000joules=29,430kw
29,430 kw /3600=8.175 kw potential
if correct
then
each time i fall i have 8 kw for an hr approx
there are more variables involved in this but this is adequate to start

1,000,000 kilos is about this size

View attachment 251933

How about 1 million liters of water? That's a lot more practical. You pump the water uphill, then make electricity as it comes down. The round trip efficiency is about 80%. We call it pumped hydro power. For that, 5 kw is pretty small.

Read more about it:
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
i have 1,000,000 kg that will drop 10 ft
10 ft of water can be pushed and pulled equating to 20 ft of water
if said weight was a barge that measured 30x100 and was in a steel chamber so all water can be ran thru a turbo or other form of weight transfer
how can i figure the potential energy in this

anorlunda
Mentor
how can i figure the potential energy in this
It is no different than the calculation you did in #12. kg of water and height in meters.

As I said before, large scale pumped hydro systems achieve 80% efficiency. The energy out is 0.8 times the energy in. As you know, power is related to how fast you put energy in or out.

Are you just curious about the physics, or do you plan to make something?

yes
i am tired of paying for energy and i have access to 1,000,000kg that rise and fall
i would like to use said energy for businesses that are energy hogs and i have access to a flywheel company to store end product and dispense it as needed
its a win win for me
i needed a simple calc to use in a plug and play calc to show the falling mass and water mass energy output for a base wattage guide to build around
it amazes me that the tonnage actually produces so little wattage but it does make sense
i love physics and all things related to science and it saddens me that the younger generation cant see the mystery and depth of it

1,000,000 kg
3 meters
g = 9.81 m/s/s
29,430,000joules=29,430kw
29,430 kw /3600=8.175 kw potential
if correct
then
each time i fall i have 8 kw for an hr approx
there are more variables involved in this but this is adequate to start
This is very sloppy with the units. If you are going to spend any time on ideas like this you need to understand the differences between forces, energy, and power.
29,430,000joules=29,430kw
No, 29,430,000 joules is 29,430 kilo Joules
Better to say 29,430,000 joules is 29,430 kilowatt-seconds (because a joule is a watt-second)
then 29,430 kilowatt-seconds divided by 3600 second per hour is 8.175 kilowatt-hours

You came to the right value in the end, but every time you write "kw" when you mean "kw-hr" fewer and fewer people who know what's going on will be paying any attention.

russ_watters
Mentor
... i have access to 1,000,000kg that rise and fall...
Wow. May I ask what that is?

russ_watters
Mentor
You came to the right value in the end, but every time you write "kw" when you mean "kw-hr" fewer and fewer people who know what's going on will be paying any attention.
Indeed, I saw the error and couldn't/didn't bother to figure out where it was really going. Good catch.

anorlunda
Mentor
yes
i am tired of paying for energy and i have access to 1,000,000kg that rise and fall
i would like to use said energy for businesses that are energy hogs and i have access to a flywheel company to store end product and dispense it as needed
its a win win for me
I moved this thread to our DIY forum.

If you are thinking about energy hog businesses, do you know their energy consumption? 8kWh at a price of $0.25/kWh is worth$2. What is the typical electric bill of those businesses you want to help? You can answer in money units, or kWh units.

Good engineering advice is to always know the requirements before starting design. Size, cost, energy requirement, power requirement, hours per day requirement, safety requirement. All those things should be known before you choose the method making electricity.

Nobody would spend 1 million dollars to save $2 per day on their electric bill. You talk about lifting masses, gearing, flywheels, and water, all those choices come after you know your requirements. Wow. May I ask what that is? if my end game is maximum wattage then the mass could be any large seagoing vessel on the puget sound and the typical container ship is well over 1 million kilos tide change every 24 hrs varies from 2 to 13 twice every day but using a formula and setting up a real world application sucks berkeman Mentor if my end game is maximum wattage then the mass could be any large seagoing vessel on the puget sound and the typical container ship is well over 1 million kilos tide change every 24 hrs varies from 2 to 13 twice every day but using a formula and setting up a real world application sucks To extract energy from that elevated mass, you will need to support it significantly above the waterline during the extraction period. How much do you think that infrastructure will cost you to build? The only other way would be to build locks on the Sound similar to the Panama Canal, and extract energy from the water flowing in and out from the sea during tide changes. But that would impede waterway traffic, which would also be a problem. Hmm... I moved this thread to our DIY forum. If you are thinking about energy hog businesses, do you know their energy consumption? 8kWh at a price of$0.25/kWh is worth $2. What is the typical electric bill of those businesses you want to help? You can answer in money units, or kWh units. Good engineering advice is to always know the requirements before starting design. Size, cost, energy requirement, power requirement, hours per day requirement, safety requirement. All those things should be known before you choose the method making electricity. Nobody would spend 1 million dollars to save$2 per day on their electric bill.

You talk about lifting masses, gearing, flywheels, and water, all those choices come after you know your requirements.
i am looking at small smelters using induction heating
puget power has special rates for large consumers so i wont qualify so ave is .10/kwh depending on time of day
the flywheel assembly that i mentioned is made by beacon power and will convert any voltage to useable voltage
they are spendy but its a nice set up to keep track of wattage made /used/still available
even if i dont use the power but want to sell it
the power companies will buy it at a reduced rate
or i could sell it to another business as long as i meet the stringent codes and procedures
the cost to raise the mass 10 ft is nothing
its a free energy give away

berkeman
Mentor
its a free energy give away
Did you read my post?

To extract energy from that elevated mass, you will need to support it significantly above the waterline during the extraction period. How much do you think that infrastructure will cost you to build?

The only other way would be to build locks on the Sound similar to the Panama Canal, and extract energy from the water flowing in and out from the sea during tide changes. But that would impede waterway traffic, which would also be a problem.

Hmm...
nope and nope
i am not looking for maximum efficiency
i looked into a linear generator to use the small distance to make the energy and it worked very well with my flywheel setup
building locks in puget sound would result in the mayor of seattle parking his kayak in the middle of it and singing cumbya
even if i had a single large chain tied to a geared drive it would work
not well,but it would work
i can get access to both shoreline and bouy points for minimal dollars
if i had access to a decent designer and a few engineers w a power point and flashy pictures
i will have investors kicking my door in
if i offer green credits
the sky is the limit

lol
do a quick search on the narrows and see what the volume of water is that races thru a very narrow channel
its staggering

Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
extract energy from the water flowing in and out from the sea during tide changes
That's a great idea. Since the mass of the water exceeds the mass of the ships, why don't we move this to somewhere without so much maritime traffic. We can also increase the efficiency by using a river instead, since then we don't need to worry about both directions. We could call it a...damn! Just slipped my mind. What was I going to call it?

Damn. Damn. Damn!