Find the mass of ice that melts during the hit.

[MaiteB]

Homework Statement

The sphere of lead with mass 2kg and velocity 20m/S hits a block of ice and is stuck in it. Find the mass of ice that melts during the hit. The initial temperature of the sphere is 293 K and c=128J/kg*grade.

Homework Equations

m1v1=m2v2

The Attempt at a Solution

I thought to use the formula but what is the v of ice?

 

[PWiz]

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]

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.

Ek=400J
Next should I write mcT=Ek? How can I find the difference in ice temperature?

 

[CWatters]

Next should I write mcT=Ek? How can I find the difference in ice temperature?

The ice doesn't change temperature. It just turns to water at the same temperature.

Is that the right equation in this situation?

 

[PWiz]

The ice doesn't change temperature. It just turns to water at the same temperature.

Is that the right equation in this situation?

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]

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.

 

[insightful]

You had better get used to having incomplete data in life. Intelligent assumptions are a part of many problem solutions.

 

[MaiteB]

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 answer is 16.5 g, if it helps

 

[insightful]

So, what are all the sources of energy available to melt the ice?

 

[MaiteB]

So, what are all the sources of energy available to melt the ice?

The sphere with its energy

 

[insightful]

And what two types of energy are available in the lead shpere?