Video Lesson

Simulation

https://phet.colorado.edu/en/simulations/energy-skate-park-basics

Lesson Objective

Dear Learners,

At the end of this section, you should be able to:

• Define and use the concepts of kinetic and potential energies;
• Solve problems related to kinetic energy and potential energy of an object.

Brainstorming Question

Can you mention some forms of energy? How can energy transform from one form to another?

key terms and concepts

Kinetic Energy

Simulation

Kinetic Energy

Kinetic energy is the energy an object possesses due to its motion. It depends on the mass (m) of the object and its velocity (v). The SI unit of kinetic energy is the Joule (J).

Formula:

• The kinetic energy (E_K ) is given by the formula: E_K =1/2mv²
• Where m is the mass of the object in kilograms (kg) and v is its velocity in meters per second (m/s).

Example:

A car with a mass of 1,000 kg is moving at a speed of 20 m/s. Calculate its kinetic energy.

Given values:

• Mass, m=1,000 kg
• Velocity, v=20 m/s

Required values:

KE=?

Solution:

E_K =1/2mv²

             =12×1,000 kg×(20m/s)²

             =1/2×1,000×400

             =500×400

        E_K =200,000J

Result:

The kinetic energy of the car is 200,000 Joules (J).

Potential Energy

Simulation

Potential energy due to gravity

Potential energy is the stored energy an object possesses due to its position or configuration. Common types include gravitational potential energy and elastic potential energy. However, in this section you are going to learn gravitational potential energy.

Gravitational Potential Energy (E_P)

Gravitational Potential Energy (E_P) is the energy stored in an object as a result of its vertical position or height above the ground. The SI unit of potential energy is the Joule (J).

Formula: E_P=mgh

Where

• m = mass of the object (in kilograms)
• g = acceleration due to gravity (9.8 m/s_² on Earth)
• h = height above the ground (in meters)

Example:

A 5 kg flower pot is placed on a shelf 2 meters above the ground. Calculate its gravitational potential energy.

Given values:

• Mass, m=5 kg
• Height, h=2 m
• Acceleration due to gravity, g=9.8 m/s²

Required values:

E_P=?

Solution:

E_P =mgh

                E_P = 5 kg×9.8 m/s²×2 m

                E_P = 98J

Result:

The gravitational potential energy of the flower pot is 98 Joules (J).