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Homework Help: A few questions about water pressure, temp, and sound

  1. Jul 5, 2005 #1
    OK.

    I have done most of them correctly on my own, I need 2 checked and help with one:

    Check:

    A sound source emits sounds of frequency 210 Hz that travel through still air at 340 m/s. The source moves away from the stationary listener at 80 m/s. Find the wavelength of the sound waves between the source and the listener.

    I got Wavelength =2m

    A small immersion heater is rated at 380 Watts. Estimate how long it will take to heat a cup of soup (assume this is 240g of water) from 23oC to 56oC

    I got t=87.2451s


    Now I need help with this one:

    A 3.8 kg block of copper at a temperature of 79oC is dropped into a bucket containing a mixture of ice and water whose total mass is 1.2 kg. When thermal equilibrium is reached the temperature of the water is 8°C. How much ice was in the bucket before the copper block was placed in it?
    (Neglect the heat capacity of the bucket.)

    I know heat gained=heat lost, so:

    3.8*(79-8)*387(heat capacity of copper) = ?

    I don`t know how to treat the mixture of ice and water. can someone please help me?
     
    Last edited: Jul 5, 2005
  2. jcsd
  3. Jul 5, 2005 #2
    Please! I truly need help before 10:00!
     
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