# Kinetic energy to thermal energy

• nickyfernandezzz
In summary, the conversation discusses a physics problem involving a lead ball hitting a wooden cube and calculating the rise in temperature of the lead ball. The initial calculation by the individual results in a rise of 38 Celsius, but the answer given by their physics lecturer is 3 Celsius. It is suggested to assume that all of the kinetic energy goes towards heating up the lead and to address the discrepancy with the lecturer in a respectful manner.
nickyfernandezzz
Member advised to use the homework template for posts in the homework sections of PF.
Hey guys, I need help with the following question.
A lead ball of specific heat capacity 130J/KgK travels with a speed of 100m/s before it hits a wooden cube fixed to floor and gets stuck inside.What will be the rise in temperature of this lead ball by the time it comes to

I attempted the question as follows,
Kinetic energy Thermal energy of
Before hitting the cube on the cube.
1/2×m×v^2 = mc(t1-t2)
1/2 × m×100^2 = m× 130×(t1-t2)
t1-t2 = 38 Celsius.

But apparently the answer I was given is 3 Celsius.
Can someone please tell me where I went wrong and how to answer the question correctly?

Thanks.

nickyfernandezzz said:
Kinetic energy Thermal energy of
Before hitting the cube on the cube.
Huh?

Is there any additional information in the problem that you may have omitted? e.g. Did any of the energy go towards heating up the wood? If all of the kinetic energy of the lead ball was used to heat up the lead, then I can't find any problem with your calculation.

Edit: I think I figured out the key to reading your statement (which I quoted above). It was written in 2 columns with the equal sign in between. So it reads:
"Kinetic energy of the lead ball before hitting the cube = Thermal energy of the lead ball after hitting on the cube."

Last edited:

TomHart said:
Huh?

Is there any additional information in the problem that you may have omitted? e.g. Did any of the energy go towards heating up the wood? If all of the kinetic energy of the lead ball was used to heat up the lead, then I can't find any problem with your calculation.

Edit: I think I figured out the key to reading your statement (which I quoted above). It was written in 2 columns with the equal sign in between. So it reads:
"Kinetic energy of the lead ball before hitting the cube = Thermal energy of the lead ball after hitting on the cube."
It doesn't say whether any energy goes to heating up of the wood. But if it does, how do I do the calculation?

nickyfernandezzz said:
It doesn't say whether any energy goes to heating up of the wood. But if it does, how do I do the calculation?
You can't ...books/sources often have errors

You say ..."But apparently the answer I was given is 3 Celsius. " ... apparently ? was the answer given 3 or 3.8... and who gave it to you?

oz93666 said:
You can't ...books/sources often have errors

You say ..."But apparently the answer I was given is 3 Celsius. " apparently ? was the answer given 3 or 3.8... and who gave it to you?
My physics lecturer gave the answer as 3 Celsius .

nickyfernandezzz said:
My physics lecturer gave the answer as 3 Celsius .

Tell him he's wrong

oz93666 said:
Tell him he's wrong
Yeah,I guess that's what I'll do. Anyway thanks for helping.

nickyfernandezzz said:
It doesn't say whether any energy goes to heating up of the wood. But if it does, how do I do the calculation?
Well, if it doesn't say, then I think it makes sense to assume all of the kinetic energy goes to heat up the lead. If it did tell you that some of the energy was used to heat up the wood, the problem would have to indicate (somehow) how much energy went to the wood and how much to the lead.
And like oz93666 indicated, it is not uncommon that incorrect answers are given.
Regarding telling your lecturer that he is wrong, it may be wise to find a kinder way to address the apparent discrepancy. :)

TomHart said:
Well, if it doesn't say, then I think it makes sense to assume all of the kinetic energy goes to heat up the lead. If it did tell you that some of the energy was used to heat up the wood, the problem would have to indicate (somehow) how much energy went to the wood and how much to the lead.
And like oz93666 indicated, it is not uncommon that incorrect answers are given.
Regarding telling your lecturer that he is wrong, it may be wise to find a kinder way to address the apparent discrepancy. :)
Yes, that seems wise.Thank you.

## 1. What is kinetic energy?

Kinetic energy is the energy possessed by an object due to its motion. It is a type of mechanical energy and is dependent on the mass and velocity of the object.

## 2. How is kinetic energy converted to thermal energy?

When an object with kinetic energy collides with another object or surface, the kinetic energy is converted to thermal energy through friction. The faster the motion and the greater the mass of the object, the more thermal energy will be produced.

## 3. What is thermal energy?

Thermal energy is the energy possessed by a substance or system due to the movement of its particles. It is a type of internal energy and is related to temperature. Heat is the transfer of thermal energy from a warmer object to a cooler object.

## 4. Can kinetic energy be converted back to thermal energy?

Yes, kinetic energy can be converted back to thermal energy through the process of heat transfer. For example, when an object with kinetic energy comes to rest, its kinetic energy is converted to thermal energy and is released into the surrounding environment as heat.

## 5. What are some practical applications of converting kinetic energy to thermal energy?

There are many practical applications of converting kinetic energy to thermal energy, such as in braking systems of vehicles, friction heating in machines and engines, and even in cooking through the use of friction from rubbing two objects together to create heat.

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