Energy New

The physics of a hydroelectric dam

Which part of the dam has the greatest impact on its power output?

Grade

Duration

40 mins

Type

Class discussion

Overview

Students examine how the power-generating mechanism of a dam can be seen as a collection of input variables leading to an output result—the power generated by the dam. Using this understanding, students rank the input variables according to their relative impacts on the output power.

Instructions

What you'll need

"The physics of a hydroelectric dam" handout , one or two for each group
"Ranking the variables" worksheet, one for each student
"Teacher’s guide" handout

Organize your students into small groups (2-4 students) and provide each student with a copy of the "Ranking the variables" worksheet.
Briefly review the general processes that generate useful energy from falling water, highlighting the four main variables that influence power output.
Invite groups to suggest connections among the four main variables of the dam and the energy it generates. Encourage students to consider Newton’s laws, kinematic equations, and mathematical thinking.
Guide your students’ attention to the second page of the worksheet, and ask them to now develop an initial conjecture about the relative impact of each input variable on the amount of electrical power generated by the dam. Prompt groups to note their rankings and thinking on the worksheet.
Encourage groups to share their rankings and thinking with the class. As students share, help them see the relevance of slope in this determining impact. At this time, allow students to share incomplete or inaccurate rankings for they will revisit their initial conjectures later in the activity.
Provide each group with one or two copies of the "The physics of a hydroelectric dam" handout. Briefly explain that the challenge of this activity is to determine the relative impact of each input variable on the power output of a dam.
Ask groups to carefully consider the information on the handout, then rank the impact of each input variable. Prompt groups to note their rankings and justifications in the “Thinking after considering the physics” section of the worksheet. For more information on how the variables might be ranked, please see the "Teacher's guide".
Invite groups to share their rankings and thinking with the class. As students share, ask students if a ranking of the variables appropriate at all? Why or why not?

Modify or extend this activity

Extension

Invite your students to suggest how the force of friction might affect the rankings.
Invite students to determine how recent upgrades made to hydroelectric dams in the province may have impacted the energy output.

Modification

Provide support for the students in understanding the example in the handout by “walking through” each step of the problem and related formulae.

Curriculum Fit

Physics 11

Big ideas

Forces influence the motion of an object.

Content

Horizontal uniform and accelerated motion
Contact forces and the factors that affect magnitude and direction
Mass, force of gravity, and apparent weight
Newton’s laws of motion and free-body diagrams
Balanced and unbalanced forces in systems

Curricular competencies

Questioning and predicting

Demonstrate a sustained intellectual curiosity about a scientific topic or problem of personal, local, or global interest
Formulate multiple hypothesis and predict multiple outcomes

Processing and analyzing data and information

Experience and interpret the local environment
Seek and analyze patterns, trends, and connections in data, including describing relationships between variables, performing calculations, and identifying inconsistencies
Use knowledge of scientific concepts to draw conclusions that are consistent with evidence
Analyze cause-and-effect relationships

Evaluating

Consider the changes in knowledge over time as tools and technologies have developed
Consider social, ethical, and environmental implications of the findings from their own and others’ investigations
Assess risks in the context of personal safety and social responsibility

Applying and innovating

Contribute to care for self, others, community, and world through individual or collaborative approaches
Contribute to finding solutions to problems at a local and/or global level through inquiry
Implement multiple strategies to solve problems in real-life, applied, and conceptual situations.
Consider the role of scientists in innovation.

Communicating

Communicate scientific ideas and information, and perhaps a suggested course of action, for a specific purpose and audience, constructing evidence-based arguments and using appropriate scientific language, conventions, and representations

Assessments

Throughout the activity, assess your students’ abilities to:

Use Newton’s laws, kinematic equations, mathematical vocabulary, and other scientific concepts to describe real-life systems
Use the provided definition of “impact” to develop rankings of the variables