# A few questions about water pressure, temp, and sound

#### Scirel

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?

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#### Scirel

Please! I truly need help before 10:00!

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