Questions tagged [energy]

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-3 votes
0 answers
18 views

How to calculate force? [closed]

Hello: How would I calculate the force needed to manually reel in a thermal pool cover on a storage reel using the crank handle. Then length of the crank is about 15". The length of the handle ...
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1 answer
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Force Required to Keep Ball Rolling

I am attempting to recreate a demonstration that someone told me about. A hollow steel ball rolls around in a non-metalic bowl, electromagnets keep it going. I obtained a steel ball and a glass ...
1 vote
5 answers
61 views

Are there any ad-hoc uses for electricity that we can divert excess energy to when renewables are peaking?

My idea is this: divert excess energy that comes from peak renewable energy production to ad-hoc public works whenever we have more than we can put in batteries. I just don't know what things like ...
0 votes
1 answer
29 views

mg996r - maximum weight for robot arm

I want to build a robot arm (see https://youtu.be/F0ZvF-FbCr0) to move a dumbbell of 2 kg (roughly 2.2 lbs). However, since I have no background in engineering, I have no idea how to calculate / find ...
1 vote
2 answers
51 views

Suggestions for mechanisms for slowly releasing gravitational energy

I'm searching for a mechanism to slowly release gravitational energy. I've attached an image of an example scenario where a 10kg weight slowly raises the 1kg weight over a set period of time, for ...
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1 vote
1 answer
51 views

Principle of virtual work "geometric proof"

I spent a full day searching for and trying to understand why in this "proof" of virtual work makes sense. I've come to understand the idea from D'Alambert's principle, but I want to ...
0 votes
0 answers
45 views

Are internal combustion engine more efficient than steam turbines

From what i understand the indicated thermal efficiency of an ic engine is measured at the fly wheel and is the measure of the amount of thermal energy being converted to mechanical energy please ...
0 votes
1 answer
41 views

Calculate uphill efficiency on different gears

I was interested to find whether it would be more efficient to climb a hill on a lower gear, so I did some calculations. I have the following data of a custom vehicle: Gear Drive force (N) Max speed (...
1 vote
0 answers
29 views

What should be the clearance and creepage for the line to line 440 Vac and line to neutral 240 Vac of the three-phase system on PCB?

Also is there any link to calculate this as per the UL and other industrial standards
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2 answers
59 views

Boiling water efficiency [closed]

What is the most efficient method to boil water without thermal energy. eg. burning gas. Reducing pressure reduces the energy required but is there something on a molecular level that is the most ...
-1 votes
2 answers
57 views

Strain energy, Conservative force and Potential energy

What I know: In general, the work done by a conservative force $F$ is equal to the negative change in a potential energy. $$\int_1 ^2F.ds = - (U_2 - U_1) $$ A potential energy is always associated ...
0 votes
0 answers
41 views

What are some methods of converting electricity without the use of induction or heat?

I was trying to study exactly how current in a wire is used to do so much in our life and how the energy is converted. But the only methods I have found are by using the resistance of the conductor to ...
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2 answers
69 views

Can two microphones placed within centimeter distance together measure a distance of the sound source?

I have placed two microphones placed within 1 or 2 cm distance. They can receive and record sounds around them. I want to detect the distance of the sound source (specially human voice) and the ...
1 vote
1 answer
43 views

Changing temperature under adibiatic conditions?

Can a temperature change be adiabatic? For example if no 'heat' leaves or enters the system and we compress a fluid such that it's temperature changes is this still adiabatic? If energy is transferred ...
0 votes
2 answers
70 views

Sign Convention for Energy Methods in Vibration Analysis

Find the equivalent spring stiffness of the system below. I was able to solve it using Newton's second law and got the result below. $$ k_{eq} = \frac{mgl}{2} - \frac{k_1 l^2}{16} - k_2 l^2$$ However,...
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0 votes
1 answer
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how much energy is stored in a car under sun ? (car interior)

When a car is under the sun, the interior is hot. This is due to the interior, especially seats, which are black (or a dark color) so that they heat under sun light and restitute this heat to the air. ...
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0 votes
0 answers
42 views

Calculate the total energy required to fly drone

How much energy will drone batteries consume if I have the following inputs: By using provided GPS flight path data I've calculated total horizontal distance using the Haversine formula, and ...
2 votes
4 answers
74 views

Different equations for Hydropower

I was doing some reading in hydropower and I came across these two power equations: $$P = ρghQ $$ and $$ P = QHg $$ Q is flow rate, ρ is water density, g is gravity, h is height, and H is head. I do ...
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0 votes
2 answers
48 views

Net force exerted by spring

I want to find the exact net force exerted by the spring between pt. P and C, when it is compressed till point P with some mass, m attached to it and released (assuming spring goes to pt. C after its ...
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1 vote
0 answers
48 views

Area under Frequency response function (amplitude vs frequency)

Recently, I was plotting frequency responses of multi-degree spring-mass systems and I was wondering what does the area under the FRF (amplitude vs frequency) (or in general FFT) mean? Does it have ...
0 votes
1 answer
34 views

Total Kinetic Energy of a System with a Body Inside Another for Lagrange's Equation

Suppose a bus with mass $m_1$ moving horizontally with velocity $\dot{x}_1$, and a person with mass $m_2$ running with velocity $\dot{x}_2$ inside the vehicle. What is the total kinetic energy of the ...
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0 votes
1 answer
50 views

Heating pump/refrigerator - calculate efficiency

I'm wondering how I can calculate the overall thermal efficiency of my heating/refrigerator pump. Actually I have this AC/heating pump unit from Samsung (P/N: AR09TXFYBWKNEE). I've placed a power ...
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2 votes
3 answers
1k views

Is the main goal for wind turbines to take maximum energy for a given diameter?

If you increase the number of blades, that will increase torque, for the same RPM you get more power,...simple logic So why only three blades, is main goal for wind turbine take maximum energy for ...
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1 vote
2 answers
49 views

Energy consumed by a two-link planar manipulator with feedback control

I was carrying out a problem in which I have a fully actuated two link manipulator, so with an independent servo motor for each link that allows rotation in one direction and another (positive for ...
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5 votes
2 answers
244 views

What happens to generated electricity if it is not used?

Let's take for example hydroelectricity produced at a dam and not consumed by any household or industry... Will the electricity need to be stored? What will happen if it is not stored? Does it flow ...
-1 votes
1 answer
77 views

What is the maximum distance for eavesdropping? [closed]

There is a closed question https://physics.stackexchange.com/questions/276667/what-is-the-maximum-distance-for-eavesdropping-sound-waves on Physics Stack Exchange and I thought this might fit better ...
8 votes
4 answers
5k views

Why does "potential energy" have the word "potential" in it?

Imagine a block of mass $m$ placed on the ground. I slowly lift it up to height $h$. The work done by me on the block is $mgh$. This amount of energy is now stored in the block when it is at height $h$...
2 votes
0 answers
39 views

How do you estimate the energy of an impact?

I am trying to determine the energy of elastic stress waves generated in a solid by an impact. I have a time domain waveform from a piezoelectric transducer that was placed next to the impact site, as ...
0 votes
3 answers
94 views

How to convert car power into energy (MJ) used per km?

I am currently attempting to do an energy audit regarding how much energy my car uses per kilometer. I am not sure whether my approach to this is right, and it feels like I have made too many ...
0 votes
1 answer
64 views

Understanding "total primary energy supply"

I am trying to wrap my head around the diagram and explanation here but can not understand completely how it is computed. https://energyeducation.ca/encyclopedia/Total_primary_energy_supply For ...
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2 votes
1 answer
145 views

Converting between MMBTU and MWh

a quick question: I want to convert between MMBTU and MWh to get at emission factors from energy. I have the following information: I use the data given in 40 CFR 98 (see EPA source here) by the EPA ...
2 votes
1 answer
432 views

Dehumidification calculations

I'm looking at options for DIY dehumidification and am hoping to get a sanity check on some calculations, and verification that I'm using the right factors in the right way. As a reference point, I ...
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0 votes
3 answers
92 views

If the developing countries consumed as much energy per capita as China how much the current energy need would grow?

I recently saw this question and I immediately thought that the discussion was too limited to current energy production, it simply assumes that the amount of energy we use today is the amount of ...
2 votes
2 answers
235 views

How do 3 blade turbines come so close to the Betz Limit?

I have seen many diagrams (see attached) that indicate that modern 3 blade turbines are nearly 50% efficient, which is about 80% of the Betz limit. Betz calculated his limit based on a theoretical ...
1 vote
0 answers
37 views

Equations of motion in matrix form and energy consumption

I am working on Lagrangian derived high-dimensional motion equations for a robot in matrix form. The structure of such an equation is known: $M(q)\ddot{q}+C(q,\dot{q})\dot{q}+G(q)=0$ In here, $M(q)$, $...
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3 votes
2 answers
70 views

What are some technical problems with generating electricity using a gas turbine or combustible engine at a gas flaring site?

Numerous oil and gas exploration sites practice flaring for safety and disposal of unwanted low calorific gases. However, instead of just standalone burning the gas, why can't a gas turbine or ...
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4 votes
1 answer
436 views

What does MM prefix mean in MMtoe?

I was reading documents about energy importation and came across the following: The import was of 5,915.87 MMtoe I wonder if MMtoe = $10^6*10^6$ toe = $10^{12}$ toe. First time coming across a ...
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4 votes
1 answer
320 views

Why do monocrystalline solar cells have rounded/cropped edges?

What is the meaning of this croped part? Why do they crop it, rather than let it be full square?
1 vote
0 answers
56 views

Why do solar cells need to be square-shaped?

There were circular solar cells 30 years ago. Why do we have square-shaped solar cells now? Why square? Furthermore, Why do monocrystalline solar cells have rounded/cropped edges?
1 vote
0 answers
52 views

Why does a system with zero resultant moment turn after temporarily force-tilted?

Say a beam, 3m long from end to end, has a pivot placed at its centre of mass, at half its length i.e. 1.5m. Objects with weight 200N each are placed on both ends of the beam. The system is in ...
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1 vote
0 answers
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Why doesn't the Stress Power in the theorem of the expended mechanical power contribute to the kinetic energy?

The following is the formula of the expended mechanical power: $P(t)$ $=$ $\frac{d}{dt}$ $\int \frac{1}{2} \rho\ v^2 dV$ $+$ $\int \sigma \colon d\ dV$ where $P(t)$ is the mechanical power entering ...
0 votes
1 answer
38 views

Half-life Unit Notations

I was looking for some element's half-life, on the following website: http://nucleardata.nuclear.lu.se/toi/listnuc.asp?sql=&A1=214&A2=214&Z=88 For 214,88-Ra, the half-life is shown to be: ...
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1 vote
2 answers
46 views

How to determine energy dissipated from work applied on a load cell

I am using a load cell to see how much force people can apply on it, to help determine their health. I am integrating the force applied on the bracket in Newtons in relationship to time, giving me the ...
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1 vote
1 answer
28 views

Weibull distribution Units - ENGIEQSOL

I am using Engineering Equation Solver, and it has been telling me the units of my distribution are inconsistent. According to a the book I am reading, I think it should be unitless (as it is a ...
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1 vote
2 answers
99 views

Bernoulli equation on moving cart

Let’s say I have moving cart with velocity U . And water from pipe flows at velocity V with respect to ground The question asks to use Bernoulli equation , pressure is atmospheric in the top If I use ...
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0 votes
1 answer
51 views

Why am I getting wrong value here?

A man threw a ball with force 10 N to two displacement of 5 m and 10 m. F = ma, so let mass be 2 kg. a = 5 m/s2. Work done = 10 × 5 and 10 × 10 = 50 Nm and 100 Nm. Now, since a = 5, I assumed that ...
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1 vote
1 answer
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Can we say kinetic energy is tangential K.E?

I saw this in my textbook that $\dfrac{\text{d}K}{\text{d}t} = \dfrac{\text{d}(1/2mv^2)}{\text{d}t}= F_t v$ where $F_t$ is the resultant tangential force on the body. Now, let $F_t= F\cos\theta$ $$\...
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1 answer
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What does the author mean? Turbomachinery - Reaction

I am reading a book of Fundamental Energy Systems. The author describes the rate of change in head for a turbomachine as: $$ \frac{1}{2}[(V_1^2-V_2^2)+(U_1^2-U_2^2)+(V_{R2}^2-V_{R1}^2)] = H =U_1V_{u1} ...
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1 vote
1 answer
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Statistics on energy mix in Europe [closed]

Does anybody know where to find statistics on the energy mix in Europe (preferred by country)? I can only find the share of renewables. I'd like to see the whole mix with a split into energy sources (...
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1 vote
2 answers
54 views

Hydraulic energy recovery for high-pressure, low flow (non-steady state) conditions

What would be the best way to implement hydraulic energy recovery while de-pressurizing a pressurized volume of silicone oil initially at 1500 bar. Can a piston pump be concievably repurposed as a ...