Lesson 10: Power

Introduction

Students learn about power, perform a short lab experiment in which they calculate their own personal horse-power, and discuss how the concept of power might affect their roller coaster designs.

Learning Outcomes

• Students will understand power as it relates to work and energy
• Students will calculate their own personal horsepower

Classroom Time Required

• 90 minute (or 2 50 minute periods)

Materials Needed

• “Human Power Production” handout
• stop watches
• A stairwell with known height
• Blog post

Pre-activities

• Reassign the various roles within each team, making sure each student has a different role.

Activities

• Start the lesson by asking students whether it takes more work walk up a flight stairs or run up that same flight of stairs. Most will agree that it is “harder” to lift the object vertically, but talk with students about the fact that a person does the same amount of work against gravity in both cases (her final GPE is same). So what does “harder” mean in a physical sense? It tells us the rate at which she did work (or transferred energy from one form to another).
• Give students a definition of power and talk about units
• Do the “Human Power Production” lab with students. They can take their data in the stair well and do their analysis in the classroom.
• Following the lab, talk with student teams about how power impacts their roller coaster. Frictional power is of particular significance, because it affects the rate at which the coaster slows down (very important at the end of the ride).
• One team member needs to summarize the group’s thoughts on how power affects the ride and complete a blog post by lesson 11 (this is the last post for the project)
• If time remains, give students an opportunity to work on their final presentations (Lesson 12).

Modifications/Author Comments

• It is sometimes fun to turn the lab into a challenge. Most students will be below 1 horse power (which makes sense, as we are not horses…), so you can offer a prize to anyone who achieves a power greater than 1 hp.