## Lesson 3: Gravitational Potential Energy

## Overview:

Is the gravitational acceleration always constant? In this lesson you will explore the force of gravity for near the surface of the Earth conditions.

## Curriculum Expectations:

**Overall Expectations:**

**C3.**Demonstrate an understanding of work, energy, momentum, and the laws of conservation of energy and conservation of momentum, in one and two dimensions.

**Specific Expectations:**

**C2.1**Use appropriate terminology related to energy and momentum, including, but not limited to:

work, work–energy theorem, kinetic energy, gravitational potential energy, elastic potential energy, thermal energy, impulse, change in momentum–impulse theorem, elastic collision, and inelastic collision.

**C2.3**Use an inquiry process to analyse, in qualitative and quantitative terms, situations involving work, gravitational potential energy, kinetic energy, thermal energy, and elastic potential energy, in one and two dimensions (e.g., a block sliding along an inclined plane with friction; a cart rising and falling on a roller coaster track; an object, such as a mass attached to a spring pendulum, that undergoes simple harmonic motion), and use the law of conservation of energy to solve related problems.

## Success Criteria:

- What is potential energy?
- What is mechanical energy?
- What is gravitational potential energy?
- Derive the work done by gravity on a box as it falls vertically a height h. Is it positive or negative work? Is the object absorbing or releasing energy to the force of gravity?
- Derive the work done by gravity on a box as you lift it vertically a height h. Is it positive or negative work? Is the object absorbing or releasing energy to the force of gravity?
- The equation for gravitational potential energy represents three important points to consider. What are they and how are they useful?

## Time Allocation: 1 hour

## Learning A

ctivities:**Read**pages 177 - 180 from Nelson 4.3 and

**copy the sample problems**into your notes.

In the playlist below, video:

- Will show you how to find the potential energy gained when pushing an object upwards 8m.
- Will show you how to develop the equation of work done by gravity.

**Practice**questions 1, 2, and 3 on page 180.

## Task:

**Solve**questions 3, 5, and 7 from Nelson 4.3 Review on page 181.

## Reflect:

You lift your pet cat vertically by 2.0 m, and then you lower it vertically by 2.0 m. During this exercise, is the total work done by gravity positive, negative, or zero? Explain your answer.