Question

Classify each of the following as having potential or kinetic energy. For those identified as having potential energy, discuss how the potential energy would be realized by conversion to another form of energy. (a) gunpowder (b) a bullet in flight (c) a cell phone (lithium ion) battery (d) wind (e) a candy bar (f) spinning wind mill blades

Short answer

(a) Potential, (b) Kinetic, (c) Potential, (d) Kinetic, (e) Potential, (f) Kinetic.

Step-by-step solution

Identify Energy Type for Gunpowder

Gunpowder has chemical potential energy. This energy can be realized as kinetic and thermal energy when the gunpowder explodes.

Identify Energy Type for a Bullet in Flight

A bullet in flight has kinetic energy due to its motion. This kinetic energy is a result of the potential energy stored in the gunpowder which was converted during firing.

Identify Energy Type for a Cell Phone Battery

A cell phone (lithium ion) battery has chemical potential energy. This energy can be converted into electrical energy when the battery is used to power the phone.

Identify Energy Type for Wind

Wind possesses kinetic energy because it refers to the motion of air molecules.

Identify Energy Type for a Candy Bar

A candy bar contains chemical potential energy stored in the form of carbohydrates and fats. This energy is converted into kinetic energy and heat when consumed and metabolized by the body.

Identify Energy Type for Spinning Wind Mill Blades

Spinning wind mill blades have kinetic energy as they rotate due to wind. This kinetic energy can be transformed into electrical energy via a generator.

Key concepts

Potential Energy

Potential energy is the energy stored in an object due to its position or condition. It's like a battery that waits to be used. Depending on its state, this energy has the potential to do work.

Examples include:

• A rock perched on a hill, which has gravitational potential energy due to its elevated position.
• A compressed spring holding elastic potential energy, ready to be released.
• Gunpowder and a candy bar both contain chemical potential energy, stored in their chemical bonds. This energy is ready to be unleashed through chemical reactions.

To realize its potential energy, an object must convert it into another form of energy. For instance, gunpowder converts its potential energy into thermal and kinetic energy when it explodes.

Kinetic Energy

Kinetic energy is the energy of motion. Anything that moves possesses kinetic energy.

Common examples include:

• A bullet flying through the air. It has kinetic energy because it's moving rapidly.
• A car driving down the road or a child running in a park, both exhibit kinetic energy.
• The movement of wind, which can drive turbines and produce electricity.

The amount of kinetic energy an object has depends on its mass and speed. If an object's velocity doubles, its kinetic energy quadruples, showcasing the significant impact of speed on kinetic energy.

Energy Conversion

Energy conversion is the process of changing energy from one form to another. This concept is central to how we use and understand energy around us.

For instance:

• Gunpowder stores chemical potential energy and converts it to kinetic and thermal energy when ignited.
• A battery converts stored chemical energy into electrical energy to power devices like cell phones.
• Wind turbines convert the kinetic energy of wind into electrical energy.

Energy conversion is crucial in various applications like electricity production, automobile engines, and even our bodies consume food, converting chemical energy into kinetic energy for movement.

Chemical Potential Energy

Chemical potential energy is the energy stored in the chemical bonds of molecules. It's a subtype of potential energy specifically related to chemical substances.

Key examples include:

• A battery like those in cell phones, which stores energy that can be converted into electrical energy.
• Gunpowder, which can transform its stored energy into kinetic energy during an explosion.
• Foods such as candy bars. They contain energy in the form of carbohydrates and fats, which our bodies convert to kinetic energy when metabolized.

Chemical potential energy is vital because it powers countless everyday activities. From the devices we use, like smartphones, to the food that fuels our activities, chemical energy is a fundamental part of life and technology.