1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Temp rise due to hammering nails

  1. Jun 12, 2006 #1
    Here's my question.....

    The 1.20 kg head of a hammer has a speed of 6.5m/s just before it strikes a nail and is brought to rest. Estimate the temperature rise of a 14 gram iron nail generated by ten such hammer blows done in quick succession. Assume the nail absorbs all the energy.

    The picture shows a hammer hitting a nail with the swings being horizontal(as if you were nailing into a wall.......not the floor).

    So, I can't seem to get my formulas set to get past a certain point. This is what I've done so far(which is not much).

    W= 4.186 J = 1 cal of heat
    W = Fd
    F=ma------where I get stuck......I've got velocity, but not acceleration.

    Thanks for any help.....I'd be glad to work it with some help....or maybe I can work it a little further until I get stuck again(if I do).

  2. jcsd
  3. Jun 12, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    How much kinetic energy does the hammer possess before it hits the nail? What happens to that energy?
  4. Jun 12, 2006 #3
    Ok.....well I kinda see where you are going, but still need a bit more direction.


    KE(hammer)=25.35 J -----So I think this energy is now transfered into the nail, with some lost to heat?? Or, do I have to recaculate the KE for the nail(using its mass)?

    I'm also not real sure how this energy(J) is going end up giving me a temp measurment.....will I eventually relate it to the specific heat of iron?

    Thanks again and I'll keep working....

  5. Jun 12, 2006 #4

    Doc Al

    User Avatar

    Staff: Mentor

    What's the speed of the nail after you hit it with a hammer? (Hint: Nothing to calculate.)

  6. Jun 12, 2006 #5
    The speed of the hammer would be directly transfered to the nail.....so it would be 6.5m/s. With that in mind(and the nails mass), I found KE(nail)=.296 J

    Do I multiply 10 swings into both the KE of the nail and the KE of the hammer?? I'm thinking I do, it just seems obvious. Then I'm thinking I have to Joule measurements....so then do I multiply them both by the specific heat of iron.....and add them together to obtain a final amount of heat created?

    Thanks again!!!
  7. Jun 12, 2006 #6

    Doc Al

    User Avatar

    Staff: Mentor

    No! You bang a nail into the wall, does it goes shooting through the wall? (Let's hope not.) No, when the hammer hits, the nail moves a bit, then hammer and nail both stop. The KE of the nail is zero. (That's why I said there is nothing to calculate. :smile: )

    All of the KE of the hammer gets absorbed by the nail as thermal energy.
  8. Jun 12, 2006 #7
    Ok.....that does make sense, as I think of it more and more.

    So, now I am thinking that I multiply my KE(hammer) by 10 swings to find total KE. Then do I use an equation similar to U(internal energy) = N(1/2mv^2).....where N is number of molecules?? This doesn't seem like the right equation though. Also, I can't yet understand why they gave me the mass of the nail(and maybe that is for later in the problem).
  9. Jun 12, 2006 #8
    [tex] \frac{1}{2} m v^2 = mc \theta[/tex]
    Last edited: Jun 12, 2006
  10. Jun 12, 2006 #9

    Doc Al

    User Avatar

    Staff: Mentor


    It's not. Think specific heat of iron, which you mentioned earlier. (You'll need the mass of the nail.)
  11. Jun 12, 2006 #10
    Ok, well I am thinking this now.

    KE(total) = 253.5 J

    Q = mc*(change in T)

    Change in T = Q/mc

    253.5 J * .014 Kg * 450 J/Kg*deg C = 40.24 deg C

    Even close?
  12. Jun 12, 2006 #11
    yeah I knew they did heat up......as I used to frame houses/apartment buildings for a few yrs.......
  13. Jun 12, 2006 #12
    nevermind......ha......just noticed the problem was odd, so I checked it in the back, and I have the correct answer!!!

    Thanks a ton Doc Al!!

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Temp rise due to hammering nails
  1. Hammer smashing nail (Replies: 6)

  2. Hammer and Nail (Replies: 3)

  3. Hammer On Nail (Replies: 9)

  4. Hammer/nail Moment (Replies: 1)

  5. Hammer and nail (Replies: 2)