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. R

    Equation for force from Vf, mass, and joules?

    So I'm doing some research regarding firearms and need to know the amount of force on the bolt assembly as the bullet is fired. Using a .45 caliber Federal bullet, the mass of the projectile is 15 g, the energy is 500j, and the Vf is 260 m/s. I need to know how to convert these numbers into a...
  2. W

    How many joules expended for a push up?

    Just wondering if any of you can do the calculation that well approximates the amount of joules expended by a push up.
  3. PhizKid

    Converting joules to calories

    Homework Statement Convert 4.18 joules/(grams * Kelvin) to calories/(pound * Farenheit) (heat) Homework Equations 1 Kelvin = -272 Celcius 1 Calorie = 4.18 Joules 1 Celcius = 33.8 Fahrenheit 1 lb. = 454 grams The Attempt at a Solution \frac{4.18 Joules}{1 gram \cdot 1 Kelvin}...
  4. H

    Converting binding energy of an element to joules

    Converting binding energy of an element to joules! The binding energy of Mg-24 is 198MeV. What is this value in Joules? Write your answer correct to three significant figures. MeV = megaelectron volt 1 megaelectron volt = 1.60217646 × 10-13 joules 198 megaelectron volts = 3.17230939 ×...
  5. Z

    Ramsauer-Townsend equation. Joules or eV?

    Homework Statement There is a Ramsauer-Townsend equation in my notes for transmission. It's difficult to write out but looks somewhat like: T = {1 + {(sin k a)^2 / 4E/V0 (E/V0 - 1)}} Of course E and V0 should be in the same units. But should they both in Joules or eV? I would...
  6. C

    Converting joules into a measureable mass (lbs of weight)

    It has been a long time since I have emersed myself in physics but I am trying to write a labview program that takes into account distance, speed, mass to calculate the KE of an activity such as running a mile or shorter distances like 40 yards. With the KE I am having trouble figuring out how...
  7. P

    How can I calculate the joules for speeding objects?

    Ok,lets say an object is moving at a constant speed of Mach 7 for 20000ft. The weight for the object is 2000 lbs. What formulas could I use to calculate the energy for accelerating objects,or this one in particular?
  8. R

    The Amount of Joules generated by a car wheel travelling at 30mph

    I am interested to know the amount of Joules created by an average size car wheel traveling at 30mph. Please could you let me know the calculation needed to work this out? Thank you,
  9. D

    Calorie to Joules: Understanding the Fundamentals

    I can find the conversion easy enough, but I want to understand the fundamentals behind it. How do we KNOW that 4.184 J are in a cal? I'm learning thermodynamics and my book neglects to mention this(yet), and I'm getting hung up on it. I am having difficulty understanding how temperature...
  10. V

    Messed up joules and Newtons in an exam

    I know this is just a piece of whining, but I feel awful about it and want other's opinions. It wouldn't really bother if I didn't think I'm OK in physics. In a question I had to calculate potential energy and naturally wrote the answer down as joules. However, when I came back to check the...
  11. N

    Joules per Coulomb and the Volt

    Hey, A coulomb is the amount of charge that passes a point through a wire carrying one ampere for one second. Voltage is a measure of electrical potential energy in units of volts or joules per coulomb (energy/charge). Then 1 volt means 1 joule per coulomb; 2 volts mean 2 joules per coulomb...
  12. M

    Kinetic+potential+internal; also, Joules

    Pardon my simple question, but I'd like some general intuition on what I'm reading in the thermochemistry section of my chemistry textbook (I'm posting the question here because it seems more related to physics, but if it needs to be moved, that's OK). All right, I'm reading that: Total...
  13. M

    Finding Joules of heat for 75% efficient motor at 250hp.

    Homework Statement Forgive me for any indiscretions my first post. The problem is to find the Joules of heat per hour produced in a motor that is 75% efficient and requires 0.250hp to run it. Homework Equations efficiency=1-(Qc/Qh)The Attempt at a Solution 1. convert hp to Watts; 0.250hp*...
  14. S

    Calculating Stress in Joules: My Experience

    I have tried it and the units end up being Nm^-2 (the unit of stress) however the unit for joules is Nm.
  15. A

    How to write joules per metre squared per second

    This was a question I had in another post, but the main topic was on a similar but different issue... If I had the dimensions joules per metre squared per second (e.g. like for a solar panel), how would I write that? I've been told \frac{Js}{m^2} But I get \frac{J}{m^2s} Why is it...
  16. A

    How many joules of energy are supplied.

    Homework Statement How many coulombs of electricity pass through a lamp when a current of 5A flows for 3 minutes. Answer: 900C In this time 27,000 joules of electrical energy is converted into heat and light. How many joules of energy are supplied by each coulomb. Homework Equations V=W/q...
  17. M

    Calculating Joules from Watts: 4000 Watts for 30 Seconds

    1 Watt = 1 Joule/Second So does that mean if I input 4000 watts for 30 seconds that will output 12000 Joules?
  18. B

    How to convert the energy in Joules to mass in a metric done

    any help would be appreciated. not sure where to start.
  19. J

    Joules required to heat/how much heat is released

    Homework Statement 1.)How many joules are required to heat 250 grams of liquid water from 25 C to 100 C 2.)How much heat is released when 200 grams of steam condenses? Homework Equations q=m*(delta) t*c q=(delta)H*m The Attempt at a Solution 1.)q=250g*75°C*4.186joules ? = 74 487joules ? 74...
  20. C

    Maximizing Distance Traveled with 1200 Joules of Fuel in a Potato Cannon

    Homework Statement We are given an amount perfume, that has an energy level amounting to 1200 joules. Using this as the fuel, i need to build a potato cannon. How can i build the cannon to maximize the distance the potato travels when shot with this amount of fuel? Homework Equations...
  21. T

    Coulumbs, Joules and their relation in electronics

    Hello, I'm bit confused about relation of the two, would be really great if someone explained it. So the coulumb is said to be the force between two charges(repelling or attracting), which depends on quantity of charges and their distance. Joule is said to be force that is needed to move...
  22. J

    What is the value, in joules, of one quantum of energy?

    What is the value, in joules, of one quantum of energy? I read somewhere that it is equal to h (Planck's Constant). How much merit does this information hold?
  23. B

    How many joules are in a Mega Watt?

    Homework Statement I know that you can't convert between the two because one is the rate at which energy is produced and another is an amount of energy. I need to find out how much energy was used for 417 billion kilowatt hours. This was the amount for a year. Is there a way to get it in...
  24. BitWiz

    Exploring the Physics of Space Travel: Joules and Beyond

    I'm still having trouble with this: Generically, work = m * d^2 / t ^2 (mass, displacement, time) If to a 1kg mass at rest in space I attach a small rocket that fires with a force of one Newton for one second, at the end of that period the mass will have traveled 0.5 meters, and the rocket...
  25. N

    How many joules of heat will be delivered to the room

    Homework Statement In a heat pump, heat from the outdoors at -8.00 deg c is transferred to a room at 22 deg c, energy being supplied by an electrical motor. How mnay joules of heat will be delivered to the room for each joule of electrical energy consumed, ideally? Homework Equations...
  26. BitWiz

    The Relationship Between Newtons and Joules

    If I apply 1 Newton to 1 kilogram (at rest) for one second, it will have accelerated to 1 m/s^2 and traveled 0.5 meters. I have therefore done 0.5 J of work. Is this correct? If I apply 1 Newton to 1kg traveling at 1,000 m/s for one second, have I now done about 1,000 joules of work with...
  27. BitWiz

    Can Joules Be Converted to Newtons in Energy Calculations?

    I'm having trouble with this one: How do I convert joules to Newtons? Say I have a source of energy E that is capable of supplying 10 joules -- per second -- that I wish to use to accelerate a body. Would the energy supply then look something like this(?): E/s = 10 * 1kg * m^2 / s^2 /s...
  28. B

    Finding Work in Joules from a Piston

    A student exerts a steady force on the piston of her "master cylinder" and observes that it moves downward 3.2 cm as 10 ml of fluid moves into the "slave cylinder" and lifts a 500 g mass. She then reverses the roles of "master" and "slave" and places the 500 g mass on the piston of what...
  29. K

    Calculate the rotational kinetic energy of the Sun in joules

    Homework Statement Assume the Sun is a uniform, rigid sphere (it is spherically shaped but actually is not of uniform density nor a rigid body). The Sun rotates once every 27 days. (a) Calculate the rotational kinetic energy of the Sun in joules. (b) The luminosity (power output) of the...
  30. S

    What is the kinetic energy in joules of a 950-lb motorcycle moving

    1. Homework Statement 1. What is the kinetic energy in joules of a 950-lb motorcycle moving at 50 mph ? 2. If the speed of the motorcycle changes from 50 mph (with kintic energy K1) to 25 mph (with kinetic energy K2), what is the ratio of K1 to K2? 2. Homework Equations KE=1/2mv2...
  31. D

    Simple mechanisms to measure joules output?

    I'm tinkering with a simple heat engine and I want to experimentally measure its work output. The engine pushes a piston once per test, and I know the work done is on the order of 1 kilojoule. The problem is that the engine does the work on the order of milliseconds, but depending on the...
  32. A

    How to convert cm^-1 into erg or joules

    I'm not sure if this is the right place for this, but I can't seem to find how to convert cm^-1 into erg or joules... It's a pretty dumb question, but I can't find the answer anywhere. Thanks a lot in advance!
  33. D

    Dissipated Heat in Joules for Braking Motor with Given Parameters

    Homework Statement Motor running, brakes applied. how much heat in joules will be dissipated? mass 250 kg diameter 30 cm 3000 rpm torque 120 N-m Homework Equations W=1/2 *I *w2 The Attempt at a Solution I keep going the route of: (1)/(2)*250*.3*315 1*125*.3*315...
  34. T

    Change in Potential Energy = mgh = (9.0kg)(9.8m/s^2)(1.3m) = 116.4 Joules

    Swinging Monkey! Homework Statement A 9.0 kg monkey swings from one branch to another 1.3 m higher. What is the change in potential energy? Homework Equations Ke = (1/2)mv^2 GPE = mgh EPE = (1.2)Kx^2 The Attempt at a Solution
  35. majormuss

    Changing Units From Joules to Mega electron Volts

    Homework Statement I always have problems when changing units form Joule form to Megaelectron Volts and vice versa...whats the easiest way to find them? Homework Equations The Attempt at a Solution I always get confused at the conversion part.
  36. S

    What is the Potential Energy of a Twisted Spiral Spring?

    Homework Statement A spiral spring is twisted from its equilibrium position through θ = 7° by an average torque of 60 Nm. What is its potential energy in Joules? http://schubert.tmcc.edu/res/msu/mmp/kap8/picts/spring2.gif Homework Equations The Attempt at a Solution I am not...
  37. K

    What is the total energy in joules expended

    Homework Statement The power supplied by a certain battery is a constant 6 W over the first 5 min, zero for the following 2 min, a value increases linearly from zero to 10 W during the next 10 min, and a power that decreases linearly from 10 W to zero in the following 7 min. (a) What is the...
  38. J

    Kinetic Energy in Joules of an Object

    Homework Statement A car is traveling at a constant 60 miles per hour. What is its kinetic energy in Joules if its mass is 800 kg? Homework Equations KE = 1/2m * v2 (?) The Attempt at a Solution ½(800kg)*(26.82 m/s)2 = 287,724 kg * m2/s2 = 287,724 J I hope that looks right...
  39. D

    Joules converted to amp hours

    I just met a fellow who works in directional drilling. He has a problem when his dry cell lithium ion batteries die. It costs him $300,000 when it happens. What he needs to know is when to pull the batteries BEFORE this happens. These Double D cell batteries when connected, hold their 36 volts...
  40. I

    Calculating Energy Impact: Weight Required for 9 Joules at 1 Meter Height

    [b]1. How much weight is required to be dropped from 1 meter height so that on impact on ground will give 9 Joules of energy
  41. S

    Theoretical Armor Question - Joules Conversion

    Okay so I was poking around the wiki for the video game Fallout 3 the other day when I came across this page: http://fallout.wikia.com/wiki/T-51b_Power_Armor It has specs on the armor (keep in mind this is mostly the type of stuff the game designers make up for interesting backstory, so...
  42. S

    Maximum energy stored in the capacitor = 0.85 Joules

    Homework Statement An L-C circuit has an inductance of 0.430 and a capacitance of 0.240 . During the current oscillations, the maximum current in the inductor is 1.40 . What is the maximum energy stored in the capacitor at any time during the current oscillations? Express your answer in...
  43. S

    How Do You Convert Joules to Kilowatt-Hours for Hotel Energy Monitoring?

    To monitor the electrical energy usage of a room in a hotel, the 'Carbon Cops' install some measuring instruments. These gather data over 24 hrs as follows: - Total number of joules of energy used=20000000J (20MJ) - Voltage supplied = 240 V Convert the number of joules into kWh.
  44. T

    Joules and Kinetic Energy [units wise]

    K.E is in joules joules = 1Nm Nm = m/s² . m = m²/s² therefore k.e = 0.5mv² m²/s² = kg . m²/s² there is an extra kg. I don't see how there is the same problem with GPe GPE = m gh m²/s² = kg . m²/s² How can that be. The units of 0.5kgv² need to equal Nm...
  45. E

    Is 100 Nm Equal to 100 Joules of Energy?

    Maybe this is a stupid question but... If I have a torque value of, let's say, 100 Nm, am I right in saying that it takes 100 Joules of energy to generate that torque since 1 Nm = 1 Joule.
  46. A

    Joules required to accelerate 1kg of mass

    Homework Statement how many joules of energy are required to accelerate 1 kg of mass from rest to a velocity of 0.866c? I tried the relativistic kinetic energy equation, but I feel like it's totally incorrect. Homework Equations KE = [(m0c^2) / √(1-v^2/c^2)] - m0c^2 E = KE + m0c^2...
  47. D

    Einstein model of solids, energy in joules of one quantum

    Homework Statement the stiffness of the interatomic "spring" (chemical bond) between atoms in a block of lead is 5 N/m. Since in our model each atom is connected to two springs, each half the length of the interatomic bond, the effective "interatomic spring stiffness" for an oscillator is 4*5...
  48. G

    Convert 185 lbs, 23 in to Joules

    Homework Statement How much energy in joules lifting 185 lbs, 23 inches. Homework Equations The Attempt at a Solution
  49. B

    Calculating Velocity from Kinetic Energy: Solving for v in the r=mv/qb Formula

    A proton with a kinetic energy of 4.6×10−16 J moves perpendicular to a magnetic field of 0.26 T. What is the radius of its circular path? I know the formula is r=mv/qb. the only thing not given is v. So my question is how do I get v from Joules? I know 1 Joule=1N/m, and that N=ma, but I...
  50. D

    Help with Energy unit Joules EASY

    [SOLVED] Help with Energy unit ... Joules... EASY! Homework Statement The sun burns up 3.6 x 10^{9} kg of matter each second. Using the formula E = mc^{2}, determine how much energy the sun releases each second. [Speed of light: 3 x 10^{8} m/s] Homework Equations E = mc^{2}...
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