The problem involves a 2 kg lead sphere moving at 20 m/s colliding with a block of ice, resulting in the melting of a portion of the ice. The kinetic energy of the lead sphere before the collision is calculated to be 400 J. The energy conversion during the collision is critical, as the initial temperature of the ice affects the amount of ice that melts. Assuming the ice is at 0 degrees Celsius, the mass of ice that melts is determined to be 16.5 grams.
PREREQUISITESStudents in physics or engineering, educators teaching thermodynamics, and anyone solving problems related to energy transfer and phase changes in materials.
Ek=400JPWiz said:The lead sphere had kinetic energy before collision, but none afterwards. How much kinetic energy was this? What form has this energy been converted to?
Set up an equation with the total initial and final energies set equal to each other.
MaiteB said:Next should I write mcT=Ek? How can I find the difference in ice temperature?
Hmmm, I think the initial temperature of the ice does matter. The question does not specify that the ice is at 0 degrees Celsius. If it is at any other lower temperature, some of the energy from the 400J would bring it to the melting point and the remaining would convert the ice to water (the latent heat of fusion), so the initial temperature will clearly affect the mass of ice that melts. I think the question is incomplete.CWatters said:The ice doesn't change temperature. It just turns to water at the same temperature.
Is that the right equation in this situation?
The answer is 16.5 g, if it helpsCWatters said:You are correct. I didn't notice the initial temperature of the ice wasn't specified.
I agree the question is incomplete. You can't solve it unless you assume the ice is at zero.
The sphere with its energyinsightful said:So, what are all the sources of energy available to melt the ice?