# What is Joules: Definition and 123 Discussions

The joule ( jowl, jool; symbol: J) is a derived unit of energy in the International System of Units. It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one metre (1 newton metre or N⋅m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).

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1. ### I Confused about unit conversion involving natural units

Hello! I have an expression whose natural units are Joules, but all the terms are expressed in terms of cm##^{-1}## (it is for an atomic transition). I have a term in the expression whose units are 1/A (angstrom) and I am not sure how to convert it to what I need. On one hand, if I were to go...
2. ### Trying to understand the relationship between Newtons, Joules and Work

A force of 1 Newton times 3 meters, can that mean : a 1 kg mass pushed over 3 meters went from 0 to 1 m /s/s ?
3. ### Energy Received Physics of Sound question

I'm not sure! I'm really lost on this problem to be honest.
4. ### Small, simple way to generate 500 Joules in 15 minutes

Hey everyone, I'm looking to build a simple generator that can either produce 500 Joules and then store it in a capacitor so it can be used up over 15 minutes or something that can generate the needed 500 Joules in the span of 15 minutes so you wouldn't need to store it. The thing that needs...
5. ### Why are action and entropy unrelated?

Although I've read many papers that propose a relation between action and entropy, I've been told that there is no generally accepted relation in physics. But how/why are these concepts unrelated? What about nobel laureate Frank Wilczek? He proposes that entropy and action are closely related...
6. ### How to work out Joules needed to perform work

Hello all! First post here, and I apologize in advance if this question belongs elsewhere- I'll learn as I go. I am interested in knowing more about energy and performing work. In particular, if I have an object I would like to lift, how much energy I need to expend to do that. Take for...
7. ### The formulae for kinetic energy and Joules

The formula for kinetic energy is 0.5x kg x v^2, where v= velocity The formula for joules is kg x v^2 I don't understand why does the difference exist and what is the difference between joules and kinetic energy isnt joule the unit for energy?? Thank you guys for helping me.
8. ### How much heat in joules must be added to 0.841 kg of aluminu

Homework Statement How much heat in joules must be added to 0.841 kg of aluminum to change it from a solid at 130 °C to a liquid at 660 °C (its melting point)? The latent heat of fusion for aluminum is 4.0 x 105 J/kg. Homework Equations Q = mL Total = mc∆t + mL = m(c∆t +l) The Attempt at a...
9. ### How to calculate the Work (Joules) of lifting a book

1. I'm trying to calculate work it takes to lift 4 books, and stack them on top of each other in a 20 cm high stack. The problem reports: - 5 books are lying on the ground. They are each: 2kg, 4cm thick. Using the formula for Potential Energy (mgh), my calculations reflect it takes 8J: - Book...
10. ### Find the amount of work to move a particle from point A to B

Homework Statement How much work should be done on a point charge of q=15 nC to bring it from infinity to a distance of 3 cm from a surface of a charged sphere? Diameter of sphere is 15 cm, its surface charge density is 12 microC/cm2 Homework Equations W=deltaU=q*deltaV v=kQ/r...
11. ### How much heat in joules is needed to raise the temperature

Homework Statement How much heat in joules is needed to raise the temperature of 7.0 L of water from 0°C to 78.0°C? (Hint: Recall the original definition of the liter.) Homework Equations How much heat in joules is needed to raise the temperature of 7.5 L of water from 0°C to 87.0°C? (Hint...
12. ### Work Problem: 3 kg Brick Falling 15 m - 441 J?

Homework Statement How much work does gravity do when a 3 kg brick falls 15 m? Homework Equations W=Fx? The Attempt at a Solution I transferred the mass of the brick to weight (gravitational force) and got 29.4. I used this number for the force and the 15 for distance, or x. Does 441 J make...
13. ### Convert atomic mass into Joules

Homework Statement How much energy is created when 0,0188828901 atomic mass is converted into energy (Joule) Homework Equations E = m * c^2 speed of light = 299792458 1 atomic mass unit = 1.660539040e-27 kg 1 atomic mass unit = 931,494028 MeV 1 eV = 1,6021766208e-19 Joule The Attempt at a...
14. ### Calculating how many Joules are required to make a photon

A double covalent bond of nitrogen (N2) is 15.58eV Now let's go into a example. if i have a laser that is 477nm and i do 1240/477nm then i get 2.6eV per photon. Now if i do (15.58eV / 2.6eV) it equals ~6 photons. Now to figure out how many Joules are required for 1 photon I do (6.626*10^-34S *...
15. ### MHB Conversion KWH of energy per day to Joules in a year

What is the average power consumption in watts of an appliance that uses 6.65 kW*h of per day? 6650/24=277 W b) How many joules of energy does this appliance consume in a year? What is the conversion factors for b)?
16. ### B Energy of Up & Down Quarks in Joules: What Are They?

I am using a program that requires the energy of the up quark and down quark be given in Joules. I tried to find these values on the internet but could not find these values. Can someone please tell me what is the energy of the Up and Down Quark in Joules?
17. ### Sizing a Solar Array To Boil Water

Hello, I am having a hard time deciding the size of a solar array to boil water for a school project. Before putting any thought into the subject I simply thought that I would just take the wattage of the panels and add them up since they are added in both series or parallel and then select an...
18. ### Why is the Velocity equal to joules per kilogram?

Homework Statement Calculating the rms speed of an N2 molecule. The units I end up with are J/kg and this is equivalent to Velocity. my question is why? Homework Equations v = J / kg KE = .5mv^2 The Attempt at a Solution I tried to derive it myself using the kinetic energy formula. What I end...
19. ### Why 1 liter * atm = 101.33 joules ?

Hi ! I have been searching but i am not able to find out that is there any reason behind , why 1 liter * atm = 101.33 joules ?
20. ### Measurement standard for joules = Momentum in kilograms

Basically, I found the energy of a photon using its frequency ((6.8*10^15) and E=(3.6496394*10^-16)) and so I then used "p=E/c" to find the momentum and got 1.2173887*10^-24 however I don't know the measurement of the momentum. Is there a better equation to use to find momentum, and what would...
21. ### Energy release from 75c drop in water temp, 1L?

Hey everyone can anyone tell me how much energy is released (joules) if you take 1 liter of water at 100C and drop it down to 25C (room temp, reg pressure)? Is it significant amount? Better even how much energy is released (approximately) for every 1c drop in temp? Is the release in energy...
22. ### Convert Joules to Newtons: Get Help Here!

hi guys - this is not a homework problem. I'm way too old to be in school - I'm actually trying to solve a "real world" problem and I'm just a dumb computer scientist pretending to be a mechanical engineer. I'm working on designing a frame for a vehicle and I'm using a couple of different...
23. ### How do you calculate joules necessary to rotate an object?

NOTE: THIS IS NOT A HOMEWORK QUESTION! I merely wish to know how to calculate the force necessary to rotate an object, say of 10 kg, from a certain downward diagonal direction of 45 degrees into an upright position considering only gravity. I'll need to use some formula involving torque...
24. ### Confusion about calculating energy output.

Homework Statement I have a question that involves comparing the energy output of a laser to the energy required to make tea. I've already calculated the energy to make tea and I know what to do to find how long it takes to make the tea but I'm struggling with the energy output part. It says...
25. ### Calculating Vectors (in Joules) of an electromagnet

Good afternoon, Question: Say I have an electromagnet at a 45 degree incline from an electron beam. This electromagnet is exerting 0.75 Tesla on the beam. How can I calculate the vector that the electromagnet will exert on a particle? Note, this is for my own curiosity, not for any homework...
26. ### Converting Coulombs to Joules Without Voltage

Hi Is it possible to convert coulomb to joule without knowing volt?
27. ### How to create force of 3000 joules to push iron ball of 100gm?

Respected all my bros,, I want to creat force of 3000 joul to push the iron ball of 100 gm? The ball should go straight upto 10 meters at speed of 700 miles per sec.
28. ### Calculate Work Done by Force (152N): 1657.2J

How much work is done by the force? W= F * Δs * CosθW= (152N) * (13m) * Cos(33°) W=1976 * Cos(33°) W=1657.2 So I'm fairly confident I got this right since the answer is 1660J my question is Why would I have to round it up to 1660 to get it to Joules? I'm not really looking for help on the...
29. ### How is work measured in a vacuum?

I've just learned that work is done when a force moves something, and it's measured in joules. I've also learned that work = force x distance, but what significance does distance have? The force itself is what's being measured. In other words, if an object weighing 1kg was accelerated to...
30. ### Understanding Newtons vs Joules - Beginner

I'm trying to understand these basic concepts and I want to understand them deeply. In learning about Newtons and joules, I have a couple of questions. Please bare with me as I seek clarity. 1 netwon is the amount of force it takes to accelerate 1 KG at the rate of 1m/s^2. If a 1KG mass of...
31. ### Where to Find Energy in Joules of Particle Accelerators

I am looking to find the energy of particle accelerator beams in Joules, as the energy given in the URL here: http://en.wikipedia.org/wiki/List_of_accelerators_in_particle_physics only gives the energy of each proton. I am looking at all the particle accelerators still active today, and I have...
32. ### Joule's Expansion & Entropy Production

We all know that in free expansion of gases under adiabatic condition and keeping the temperture constant ,we get that no work is done by the gas.Moreover since del(Q)=0, del(U)=0 according to first law of thermodynamics.But we get a increase of entropy by an amount Rln2.Now the question is that...
33. ### Converting eV to Joules vs eV to V

Homework Statement Is this true? Homework Equations 1 eV = 1.6e-19 J 1 V = 1.6e-19 eV The Attempt at a Solution I did a bit of googling and it just seems strange. eV multiplied by elementary charge = Joules ev divided by elementary charge = Volts
34. ### Newtons to Watts to Joules

so basically i have calulated some forces in Newtons at one second intervals i have time - 1, 2, 3, 4, 5, ----- 5 seconds total distance - 3, 12, 27, 48, 72 ------ 162 meters total force = 1804, 1822, 1849, 1866, and 101 Newtons energy= 5411, 16'369, 27'736...
35. ### Why is Liter*atm equivalent to Joules?

Hey forum! My name's Patrick. :biggrin: I've been staring at this FOREVER, but I cannot seem to come up with an answer on my own. I've taken 1.5 semesters of physics, but I cannot figure this out. The reason I posted this in Chemistry is because I realized that the R constant can be written as...
36. ### Calculating Joules from Watts for Microwave Capacitor

How can a microwave I took apart have a .9 microfarad capacitor rated for 2100v? The microwave is rated at 1800 watts. What am I missing? 1/2 CV*2=1.98 joules
37. ### Calculate the work in Joules by the Acetylene gas

Homework Statement A quantity of 4.50 g CaC2 is reacted with an excess of water at 298K and atmospheric pressure. CaC2 (s) + 2 H2O (l) --> Ca(OH)2 (aq) + C2H2 (g) Calculate the work done in Joules by the Acetylene gas against the atmospheric pressure.[/B]Homework Equations After asking my...
38. ### [Problem] Elastic potential energy

Hi, I'm a second year Design Engineering student. This year we're having some basic physics class. We're doing projects on potential energy at this moment. I'm having a problem with the following; The assignment: The teacher assigned us that only 6 Joules of potential energy may be used to...
39. ### Calculating Efficiency of Electric Vehicle

Homework Statement For the following calculations, assume a typical electric car will need to apply a constant forc of 165 N to maintain a typical highway speed of 100 km/hr (27.7778 m/s). A: What power (watts) is needed to maintain this speed? B: What energy (Joules) is needed to travel 100...
40. ### Problem converting joules to dynes

I have this question: 1. The problem Convert 200 Btu to (a) BG (British gravitational), (b) SI and (c) cgs The Attempt at a Solution (a) and (b) are fine I got 155600ftlb and 200kJ but the answer the sheet gives for cgs is 211x10^10 dyne but surely the answer is 211x10^10 erg?! I can correctly...
41. ### Torque & Joules: Fact or Fiction?

Wikipedia says that the unit of magnetic dipole moments is calculated by Joule/B that means that the torque is measured by joules I really doubt that, it seems non sense.
42. ### Convert Joules to Calories - 1 cal = 4.184 J

Homework Statement 1 calorie is the energy needed to raise the temperature of 1 gram of water by 1 degree Celcius, i.e., the specific heat of water is 1 calorie/g-°C. How many joules is 1 calorie? Homework Equations ΔU = nαkΔT The Attempt at a Solution I attempted to use...
43. ### What is the measurement of work in joules?

Homework Statement If I push on a chair with 20 Newtons of force, but it doesn't move, I have done _____ of work. a. 20 joules b. 200 joules c. zero joules d. 100 joules Homework Equations W=Force x Displacement The Attempt at a Solution 0 joules =20x0
44. ### Why is heat measured in joules?

My limited knowledge tells me that joules= Newton.meters " W = F.d How can this equation be related to heat since this equation depends on force done for a certain displacement which seems unrelated to heat, when something produces heat where is this such force and displacement ?
45. ### Joules to Frequency Problem

Hi guys, I'm new to the forum, and I was recently asked this question by my friend: If a light wave has 2.50x10 to the -14 Joules of energy, what is its frequency? I'm no good at physics, so I was wondering if you guys could give me a hand. I'm completely clueless. Thanks...
46. ### Confused about torque vs. energy (Joules)

Homework Statement Solid disk, 50cm in diameter, with a mass of 5kg. Disk is located in space by a bearing. The friction torque of the bearing is 10Nm. A string is wrapped around the disk and connected to a weight. The weight is allowed to fall and spin the disk. How much energy is lost to...
47. ### How does E=MC^2 convert to Joules?

How does E=MC^2 convert to Joules? How can the speed of light measured in m/s and mass measured in grams convert to joules?
48. ### Is this a valid Joules formula?

Is this a valid Joules formula anyone has heard of? It seems to work for the few examples I have written down. I'm just curious if anyone has seen it before. I came up with it trying to equate volts to joules but had to include a function of time (via resistance) to make it work, i.e. this...
49. ### Find q(system) in joules

Homework Statement OCl–(aq) + Cl–(aq) + 2H+(aq) Cl2(aq) + H2O ΔrH = -202 kJ mol–1 25.0mL of a solution 0.400mol L–1 in both OCl– and Cl– was reacted with excess hydrochloric acid. The mass of the solution after mixing was 100 g. n(reaction) = 0.0100 mol Find q(system) in joules. Assume that...
50. ### Help Tyler with 50M Joules - What Can It Do?

To those who could help me out, I'm pretty rusty with physics I thought maybe one of you energy specialists or physics prodigies could give me an estimate at what I'm looking at. ~50million jouhls could be used for what kind of push or power would I get from this energy, would it be...