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!

Thermal properties of matter caluculation

  1. Nov 6, 2007 #1
    A squash ball of mass 46g is struck against a wall so it hits with a speed of 40m/s, and rebounds with a speed of 25m/s.
    Calculate the temperature rise (s.h.c. of rubber is 1600J/kg/K)

    This is fine. I use the equation:

    heat energy = mass x shc x temperature change

    (40 - 25) = 0.046 x 1600 x temperature change

    15/73.6 = temperature change

    temperature change = 0.2K

    Then it asks why is it unecessary to know the mass?

    And I cannot for the life of me think why. Is there another equation I'm supposed to know? Have I made a mistake? Am I overlooking something incredibly obvious?

    Any help/hints would be very much appreciated.

    Thanks,
    Rachael
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 6, 2007 #2

    Astronuc

    User Avatar

    Staff: Mentor

    The part of the solution (40-25) is not the heat energy. It's best to write units with the corresponding values.

    The 40 m/s - 25 m/s is simply the change in velocity (which is also the change in specific momentum). The change in energy is the change in kinetic energy and KE = 1/2 mv2. But looking at the righthand side one multiplies the mass * specific heat.

    If we deal with the specific kinetic energy and specific heat, we can eliminate mass from the equation. Thus

    [itex]\Delta[/itex]v2/2 = shc*[itex]\Delta[/itex]T
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Similar Discussions: Thermal properties of matter caluculation
  1. Thermal Properties (Replies: 11)

  2. Thermal properties (Replies: 11)

Loading...