Question

W is the work done on the system, and K, U, and Eth are the kinetic, potential, and thermal energies of the system, respectively. Any energy not mentioned in the transformation is assumed to remain constant; if work is not mentioned, it is assumed to be zero.

1. Give a specific example of a system with the energy transformation shown.
W→ΔEth

2. Give a specific example of a system with the energy transformation shown.

a. Rolling a ball up a hill.
b. Moving a block of wood across a horizontal rough surface at constant speed.
c. A block sliding on level ground, to which a cord you are holding on to is attached .
d. Dropping a ball from a height.

Answer 1

The example of the energy transformation W→ΔEth is rubbing your hands together, where work transforms into thermal energy. For the various scenarios: rolling a ball up a hill shows kinetic to potential energy transformation, moving a block on a rough surface showcases work to thermal energy, pulling a sliding block turns work into kinetic energy, and dropping a ball illustrates potential to kinetic energy transformation.

Step-by-step explanation:

The energy transformation W→ΔEth refers to the process where the work done (W) on a system leads to an increase in its thermal energy (ΔEth). A specific example of this transformation is rubbing your hands together. The work done by the force of your muscles creates friction between your hands, and this friction, in turn, generates heat, increasing the thermal energy of your hands.

For the various scenarios listed:

• a. Rolling a ball up a hill: Kinetic energy is being transformed into potential energy.
• b. Moving a block of wood across a horizontal rough surface at constant speed: Work is being transformed into thermal energy due to friction.
• c. A block sliding on level ground, to which a cord you are holding on to is attached: Work is being transformed into kinetic energy.
• d. Dropping a ball from a height: Potential energy is being transformed into kinetic energy.

Answer 2

1) a block going down a slope

2) a) W = ΔU + ΔK + ΔE, b) W = ΔE, c) W = ΔK, d) ΔU = ΔK

Step-by-step explanation:

In this exercise you are asked to give an example of various types of systems

1) a system where work is transformed into internal energy is a system with friction, for example a block going down a slope in this case work is done during the descent, which is transformed in part kinetic energy, in part power energy and partly internal energy that is represented by an increase in the temperature of the block.

2)

a) rolling a ball uphill

In this case we have an increase in potential energy, if there is a change in speed, the kinetic energy also increases, if the change in speed is zero, there is no change in kinetic energy and there is a change in internal energy due to the stationary rec in the point of contact

W = ΔU + ΔK + ΔE

b) in this system work is transformed into internal energy

W = ΔE

c) There is no friction here, therefore the work is transformed into kinetic energy

W = ΔK

d) if you assume that there is no friction with the air, the potential energy is transformed into kinetic energy

ΔU = ΔK