Joule's Apparatus and Kinetic Energy

In summary, Joule's apparatus is used to convert the potential energy of two falling blocks into internal energy, which is measured by the increase in temperature of the water. The kinetic energy of the falling blocks is also taken into account in the experimental design and final calculation. However, the water also gains rotational kinetic energy and there are issues with calorimetry. Joule's experiment disproved the previously accepted calorimic theory of heat and showed that heat is a form of energy, not a substance.
  • #1
Bennigan88
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In my textbook, Joule's apparatus (two blocks falling from height h turn a paddle that stirs and increases the internal energy of water) is claimed to convert the potential energy of the two blocks into internal energy that can be measured by the increase in temperature of the water... but what happens to the kinetic energy of the blocks as they are falling? They have velocity and mass so there must be kinetic energy, how is that accounted for in the setup of the apparatus?
 
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  • #2
That has to be factored into the experimental design and the final calculation of course. If your book claimed that all the falling energy becomes heat then your book is in error - but I suspect they do not make such a claim.

The kinetic energy of the blocks is less than if there was no water... they fall slower.
The water also gains rotational kinetic energy, and there are issues with calorimetry.
All these can be taken into account in a careful setup. Joule worked out the mechanical energy deficit and demonstrated that this was consistent with the heat increase in the water. The experiment more easily disproves the, then accepted, calorimic theory of heat that treated heat as a substance in it's own right.
See also:
http://www.eoearth.org/article/On_the_Mechanical_Equivalent_of_Heat_(historical)
 

1. What is Joule's apparatus and how does it work?

Joule's apparatus is a device used to measure kinetic energy. It consists of a falling weight that is connected to a pulley and a rotating drum. As the weight falls, it turns the drum and the amount of work done by the falling weight is measured by the number of rotations of the drum.

2. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is dependent on the mass and velocity of the object, and is calculated using the formula KE = 1/2 * m * v^2, where m is the mass and v is the velocity of the object.

3. What are the units of measurement for kinetic energy?

Kinetic energy is typically measured in joules (J) in the SI unit system. However, it can also be measured in other units such as calories, foot-pounds, or electron volts.

4. What is the relationship between Joule's apparatus and the law of conservation of energy?

Joule's apparatus is used to demonstrate the law of conservation of energy, which states that energy cannot be created or destroyed, only transferred from one form to another. In this experiment, the potential energy of the falling weight is converted into kinetic energy, which is then measured by the rotating drum.

5. What are some real-life applications of Joule's apparatus and kinetic energy?

Joule's apparatus and the concept of kinetic energy have many real-life applications, such as in the design of roller coasters, cars, and other forms of transportation. They are also used in renewable energy sources like hydroelectric power plants, where the kinetic energy of falling water is converted into electricity.

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