Question

Indicate whether each of the following statements describes potential or kinetic energy: a. water at the top of a waterfall b. kicking a ball c. the energy in a lump of coal d. a skier at the top of a hill

Short answer

a. Potentialb. Kineticc. Potentiald. Potential

Step-by-step solution

Identify the energy of water at the top of a waterfall

Potential energy is stored energy due to an object's position or state. Since the water is at the top of the waterfall and has the potential to fall, it possesses potential energy.

Determine the energy involved in kicking a ball

Kinetic energy is the energy of motion. When you kick a ball, you are applying a force that sets the ball in motion. Thus, this action describes kinetic energy.

Classify the energy in a lump of coal

Potential energy can also be chemical energy stored within a substance. The lump of coal contains chemical energy that can be released during combustion, making it potential energy.

Analyze the energy of a skier at the top of a hill

Potential energy is due to an object's height. A skier at the top of a hill has gravitational potential energy because of their elevated position.

Key concepts

Potential Energy

Potential energy is stored energy due to an object's position or state. It is the energy that has not yet been used but has the capability to do work in the future. Here are a few examples to help you understand better:

• Water at the top of a waterfall: The water has potential energy because it is positioned higher and can fall.
• A skier at the top of a hill: The skier has gravitational potential energy because their position on the hill gives them the potential to slide down.

This type of energy is essential in various physical processes and is fundamental to the law of conservation of energy.

Kinetic Energy

Kinetic energy is the energy of motion. Any object that is moving has kinetic energy. The more massive the object and the faster it moves, the more kinetic energy it has. For instance:

• Kicking a ball: When you kick a ball, your foot transfers motion energy to the ball. This motion is kinetic energy.

It's important to note that kinetic energy can transform back into potential energy and vice versa, showing their interdependence. The formula to calculate kinetic energy is \( KE = \frac{1}{2}mv^2 \), where \( m \) is mass and \( v \) is velocity.

Chemical Energy

Chemical energy is a form of potential energy stored in the bonds of chemical substances. This energy is released during chemical reactions, such as combustion. Here’s a classic example:

• The energy in a lump of coal: Coal contains stored chemical energy that can be released when it burns. This combustion process releases energy that can be used for heat or electricity.

Understanding chemical energy is vital for comprehending various biological and chemical processes on a molecular level.

Gravitational Potential Energy

Gravitational potential energy is a type of potential energy related to an object's height above the ground. The higher an object is, the more gravitational potential energy it has. Here are some examples for clarity:

• Water at the top of a waterfall: The water has a high position, meaning it has gravitational potential energy before it falls.
• A skier at the top of a hill: The skier has gravitational potential energy due to their height and can gain speed when they ski down.

The formula to calculate gravitational potential energy is \( PE = mgh \), where \( m \) is mass, \( g \) is the acceleration due to gravity, and \( h \) is height.