Simple Energy-Force-Distance Challenge

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Discussion Overview

The discussion revolves around the feasibility of lifting a 100 kg weight to a height of 5 meters using a power source rated at 2,943 Watts. Participants explore the relationship between power, energy, and the requirements for lifting the weight, addressing both theoretical and practical aspects of the problem.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether it is possible to lift 100 kg with 2,943 Watts, suggesting that the force provided by this power is insufficient based on their calculations.
  • Another participant clarifies that Watts is a unit of power, not energy, and emphasizes the need for 4,900 Joules of energy to lift the weight 5 meters.
  • A suggestion is made to use mechanical advantage, such as a multi-loop pulley, to increase force while decreasing velocity, allowing the lift to occur over a longer time frame.
  • Some participants argue that theoretically, any weight can be lifted with a small amount of power if given enough time, but practical limitations such as efficiency losses are acknowledged.
  • One participant expresses confusion about the relationship between power and energy, stating that they believe they only have 2,943 Joules available for lifting the weight, leading them to conclude that lifting is impossible.
  • Another participant attempts to clarify the misunderstanding regarding the definitions of Joules and Watts, reinforcing the distinction between energy and power.
  • There is a discussion about the implications of having limited power for a specific duration, with some participants suggesting that this limitation affects the ability to lift the weight as intended.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between power and energy, with some asserting that lifting is impossible with the given power and others suggesting that it is theoretically possible if time is not a constraint. The discussion remains unresolved regarding the practical implications of these concepts.

Contextual Notes

There are limitations in the participants' understanding of the relationship between power and energy, with some confusion about the definitions and implications of these terms. The discussion also highlights the need for clarity in formulating physics-related questions.

Who May Find This Useful

This discussion may be useful for individuals interested in understanding the basic principles of power and energy in physics, as well as those exploring mechanical advantage in lifting scenarios.

randy27
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Hello,

I am not a physics student, and I have a simple question/challenge.

I want to lift 100kg from the floor by 5 meters. I have 2,943 Watts of power to do this. Is it possible?

As i understand this is not possible. The force that 2,943 Watts provides is 588,6 Newtons using the formula: Energy[2,943]=Force[588,6]/Distance[5m].

Is this correct? Is there any way to use the 2,943 Watts of power to lift 100Kg?

Thanks for your help!
 
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randy27 said:
I want to lift 100kg from the floor by 5 meters. I have 2,943 Watts of power to do this. Is it possible?
Watts is a unit of power (energy per unit time) not energy; energy is measured in Joules.

As i understand this is not possible. The force that 2,943 Watts provides is 588,6 Newtons using the formula: Energy[2,943]=Force[588,6]/Distance[5m].
Your equation doesn't make sense. Perhaps you are thinking of Energy = Force*distance?

You need about 980 Newtons of force to directly lift 100 kg. To lift it 5 meters will require 4900 Joules of energy.
 
Just gear your power source so that force is increased while velocity is decreased, for example a multi-loop pulley would work just fine.

As mentioned, it will take 4900 watt x seconds to do the lift.

Since you have 2943 watts as a power source, it needs to be setup so that it takes (4900/2943) 1.665 seconds or longer to lift the 100kg weight 5 meters.
 
Sorry for clarity sake

Well, maybe I set out the problem wrong. I simply wanted to know if I can lift 100kg with 2,943Watts.

I know the units are of different type but I would like to know if I could in theory or even in practice lift the weight in any way with the energy provided in Watts.
 
(in your problem) power says only how much time takes to lift smt. i.e. you can lift anything you want , but it takes a specific amount of time as Jeff Reid calculated. So the answer is yes theoritically(but still watt is not unit of energy;)
 
Are we suggesting that a small amount of electricity power can lift a large weight? Time is not an issue so if it takes a second, a minute or an hour it does not matter.
 
Again, watts is power and lifting a weight requires energy. So since energy is power times time, you can essentially take an arbitrarily small amount of power for an arbitrarily long time and lift any weight any distance. There are, of course, practical limiting factors such as friction and other efficiency losses and the universe ending before you lift your weight to the specified height if the power is too low, but you get the idea.

For example, if you want to lift 100 kg 5m, that's 4900 n-m or joules (energy is force times distance). So since watts is joules per second, you can do that amount of work in 1 second with 4900 watts or 5 seconds with 980 watts or 4900 seconds with 1 watt, etc.
 
I can see my limitation that I only have 2,943 Watt of electricity in total. Sorry if I was not clear. Know nothing of physics and you are all helping me a great deal.

I don't have an infinite electricity capability. 2,943 Watt is my limit. This is the equivalent of 2,943 joules that I have in total, which will not get my 100kg weight up 5m.

So I would be correct to say it is impossible.
 
randy27 said:
I can see my limitation that I only have 2,943 Watt of electricity in total. Sorry if I was not clear. Know nothing of physics and you are all helping me a great deal.

I don't have an infinite electricity capability. 2,943 Watt is my limit. This is the equivalent of 2,943 joules that I have in total, which will not get my 100kg weight up 5m.

So I would be correct to say it is impossible.

No, I think you're not quite clear on what the previous posters have said. Maybe this will help. What is the answer to this question:

Say I can only drive my car 10 miles an hour. Is it possible for me to drive 1000 miles?
 
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  • #10
not if the fuel runs out, I am limited on that. So if my electricity runs out...
 
  • #11
randy27 said:
2,943 Watt is my limit. This is the equivalent of 2,943 joules
Incorrect.

Hint: look up the definitions of "joules" and "watts". Pay attention to the answers you've been given above.
 
  • #12
I still think it is I who has formulated the question all wrong due to my ignorance. Once again thank you for your patience.

One Watt is a measuremente equal to one joule per second.

The TOTAL amount of electricity available to me is 2,943W for ONE second only. So that means I have potentially 2,943 joules to spend to lift my weight. Thus i will not be able to lift my weight of 100kg up 5 meters.
 
  • #13
randy27 said:
not if the fuel runs out, I am limited on that. So if my electricity runs out...

But I didn't say anything about fuel! I only said that my velocity is limited to 10 miles an hour. Given only that information, is it possible for me to drive 1000 miles?
 
  • #14
Of course, it just takes longer. I appreciate what you are saying. I do believe I solved my problem. Unless somebody objects to

The TOTAL amount of electricity available to me is 2,943W for ONE second only. So that means I have potentially 2,943 joules to spend to lift my weight. Thus i will not be able to lift my weight of 100kg up 5 meters.

I think I cracked it. I don't do physics, but its sure uselfull! In fact... necessary :)
 
  • #15
randy27 said:
I still think it is I who has formulated the question all wrong due to my ignorance. Once again thank you for your patience.

One Watt is a measuremente equal to one joule per second.

The TOTAL amount of electricity available to me is 2,943W for ONE second only. So that means I have potentially 2,943 joules to spend to lift my weight. Thus i will not be able to lift my weight of 100kg up 5 meters.
You never said before that you only had that power available for one second. I still think you are confused about the difference between energy and power. If that is truly what you are looking for then yes, you don't have enough energy available - but besides the inconsistencies, you have also shown some pretty specific misunderstandings of the concepts of energy and power. Make sure you undersand what this thread has taught before just discarding it...
 
Last edited:
  • #16
Thank you for your help. I am totally ignorant in the subject of physics. I am very impressed with the help you have provided and although I am not a student of any kind of physics I will review my ideas on this matter.
 

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