If the temperature does not change, the change in temperature does not occur

Recall the concept of mechanical energy and its unit of measurement from your mechanics class. Review the new material. Answer the questions.

What we learned about energy in mechanics class

We learned that the potential energy of a body (such as an apple) at $h$ above the ground is given by

E_{p} = m g h

When an apple starts to fall from the top of a tree, the potential energy of the apple decreases as the apple gets closer to the ground. However, the energy cannot simply disappear. As the falling apple increases speed, its potential energy becomes kinetic energy. Since the law of conservation of mechanical energy holds

E = E_{k} + E_{p} = const

the kinetic energy of an apple hitting the ground is $E_{k}$

E_{p} = E_{k}

We also learned that energy is measured in joules (denoted by $J$ ).

So, for example, if an apple weighing $200 g$ falls to the ground from a height of $5 m$ , the energy of its motion just before it reaches the ground is

E_{k} = m g h = 0, 2 \cdot 10 \cdot 5 = 10 J

In both mechanics and thermodynamics, we measure energy in joules. In mechanics, for example, joules measure the energy of motion, whereas in thermodynamics, we use joules to measure the heat given to or taken from bodies (or heat flux, or heat energy). In everyday situations, all mechanical energy is converted into heat, and $1$ joule of kinetic energy becomes $1$ joule of heat, so the law of conservation of energy applies here too.

Describe how energy is transformed from one kind to another in the situation shown in the photograph.

Suppose we drop our aluminium test piece from a height of

10

against a table. How much would the temperature of the test object rise if all of this mechanical energy were converted into the internal energy of the test object?

Set up an experiment that would allow us to observe, or even measure, that bodies rubbing against each other get warmer.

How high would you have to drop a raw piece of meat to get it more or less cooked when it reached the ground?