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kym02

The specific heat capacity of water= 4200 J kg-1K-1 1) How much heat energy is required to warm a) 1 kg of water from 14°C to 15°C; b) 5 kg of water from 14°C to 15°C; and c) 5 kg of water from 14°C to 22°C. THANK YOU!!

  • 11 months ago
  • 11 months ago

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  1. kym02
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    \[J kg ^{-1} K ^{-1}\] this is the correct way of writing the unit

    • 11 months ago
  2. AravindG
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    Use the formul heat required =\(mc \Delta t\)

    • 11 months ago
  3. chmvijay
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    q=McDelta T

    • 11 months ago
  4. AravindG
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    where m is mass c is specific heat capacity ,delta t=change in temperature

    • 11 months ago
  5. kym02
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    ok thanks

    • 11 months ago
  6. AravindG
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    yw :)

    • 11 months ago
  7. kym02
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    i worked it out...is the answer 4200J

    • 11 months ago
  8. AravindG
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    a b or c?

    • 11 months ago
  9. kym02
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    for a)

    • 11 months ago
  10. AravindG
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    right !

    • 11 months ago
  11. kym02
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    hmm and b) is 21000J while c) is 1.68*10\[1.68\times10^{5}\] am i right???

    • 11 months ago
  12. AravindG
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    yep :)

    • 11 months ago
  13. kym02
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    was it that simple?

    • 11 months ago
  14. kym02
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    question 2! one way to measure the energy contained in a beam of x-rays is to absorb the beam by a piece of pure graphite. If x-rays are shone on to a cavity in a block of graphite of mass 10 g (0.01 kg), and a rise in temperature of 0.005K, work out the energy supplied by the beam.

    • 11 months ago
  15. kym02
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    oh and the specific heat capacity of graphite is 600\[J kg ^{-1}K ^{-1}\]

    • 11 months ago
  16. AravindG
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    same formula !

    • 11 months ago
  17. kym02
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    ok......just making sure. question 3! An electric drill consuming energy at a rate of 200 W is used to make a small hole in a block of copper of mass 2 kg. Assuming that 80% of the electrical energy used ends up in the block as heat, and that this heat is spread evenly throughout the block, estimate its rise in temperature in 10 seconds.

    • 11 months ago
  18. austinL
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    Why dont you make a new question? rather than lump several into one post?

    • 11 months ago
  19. luckythebest
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    ok @kym02 i'll give a brief info. so energy is 200 W i.e. it uses 200 J in 1 second, correct?

    • 11 months ago
  20. kym02
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    um i honestly dont know....im a beginner. Dont really know about this stuff! sorry!

    • 11 months ago
  21. luckythebest
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    Ok, then there is one concept. W means Watt. Watt is the unit of power of a machine. We say that the power of a machine is the amount of work it can do in 1 second.(i.e. rate of doing work,) Hence its unit is Watt(W) also expressed as Joule/second. so 200 W basically means that the machine will use 200 Joules of energy in 1 second. Ok?

    • 11 months ago
  22. kym02
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    ok i understand.

    • 11 months ago
  23. luckythebest
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    Fine. so if the machine uses 200 Joules of energy in 1 second, how much of energy would it use in 10 seconds?

    • 11 months ago
  24. kym02
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    2000 J.

    • 11 months ago
  25. luckythebest
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    Ok. 2000 J is the electrical energy used. Now he says that 80% of this 2000 J is used as heat energy. So what is 80% of 2000 ?

    • 11 months ago
  26. kym02
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    1600

    • 11 months ago
  27. luckythebest
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    Thats right. So this 1600 is the heat energy. As shown above, Heat energy = Mass x sp. heat capacity x rise in temp. You have mass = 2 kg, sp. heat capacity(c) = 400 JKg^-1K^-1, can you find the rise in temperature?

    • 11 months ago
  28. kym02
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    i dont know that one, do i have to transpose?

    • 11 months ago
  29. luckythebest
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    Yep you have to. above there was a formula mentioned Heat energy = m x c x delta T Here Heat energy = 1600, m = 2 kg, c = 400 J/KgK, u need to find delta T

    • 11 months ago
  30. luckythebest
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    m means Mass; c means specific heat capacity and delta T means the rise in temperature.

    • 11 months ago
  31. kym02
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    \[E _{H}=mcΔT\] so the temperature rise will be: EH divided by mass times c am i right?

    • 11 months ago
  32. luckythebest
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    Thats perfectly correct. Just type d ans also when you find it. :)

    • 11 months ago
  33. kym02
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    ok i will, im working on it

    • 11 months ago
  34. kym02
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    Is the answer 2°C?

    • 11 months ago
  35. luckythebest
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    Yes. :)

    • 11 months ago
  36. kym02
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    yes!!!!! thanks :) i have one more question though

    • 11 months ago
  37. kym02
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    a)How much potential energy does a 2.0 kg lump of copper possess when it is lifted 3.0 m from the ground? (Take g to be 10 N kg^-1.) b) If it is dropped, how much kinetic energy will it have just before it hits the ground? c) If all that energy is converted to heat, and if all that heat goes into the copper, what rise in temperature would you expect? That's all ! :)

    • 11 months ago
  38. luckythebest
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    a) m = 2, h = 3, g = 10. Use Potential Energy = mgh. b) Potential Energy found in a) = Kinetic Energy (By law of conservation of energy) c) Whatever PE you get, assume that as heat energy, the use C , M of copper to find rise in temp by formula EH = m.c. delta T.

    • 11 months ago
  39. kym02
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    whats the unit for a) ???

    • 11 months ago
  40. luckythebest
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    a) Any form of energy, whether potential energy, electric energy, heat energy, is expressed in joules( J ) (Please please note this fact; )

    • 11 months ago
  41. kym02
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    ok ok so a) =60 J

    • 11 months ago
  42. luckythebest
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    Thats correct.

    • 11 months ago
  43. kym02
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    and c) = \[7.5\times 10^{-2} \deg C\]

    • 11 months ago
  44. luckythebest
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    Which is correct, :)

    • 11 months ago
  45. luckythebest
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    I hope you're familiar with law of conservation of energy right?

    • 11 months ago
  46. kym02
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    no but i will just look back in a textbook! thank you soooo much!!! you saved me!! :)

    • 11 months ago
  47. luckythebest
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    yeah no probs as long as you're familiar with concepts and numericals :)

    • 11 months ago
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