Running on Water: Activating Prior Knowledge of Static Equilibrium

By Phoebe Jackson, John Abbott College

At a Glance

Discipline

  • STEM
  • Physics

Instructional Level

  • College & CEGEP

Course

  • Sports and the Design of Sporting Equipment

Tasks in Workflow

Social Plane(s)

  • Individual
  • Group
  • Whole Class

Type of Tasks

  • Discussing
  • Analyzing

Technical Details

Useful Technologies

  • Video player with good speakers

Class size

  • Small (20-49)

Time

  • Single class period (< 90 mins)

Inclusivity & Accessibility

  • Variety of action & expression

Instructional Purpose

  • Preparation & knowledge activation

Overview

This activity aims to activate students prior knowledge of balancing forces and then to introduce them to the concepts of free body diagrams and static equilibrium. It is particularly valuable to students because it it gets them discussing the concepts, first with their own words, interests (sports) and life experiences and then with the accepted physics terminology and laws of physics, thus easing their way into the culture of physics.

In this activity, the whole class watches a short video about running on water after which, in teams, they discuss whether the video is real or a hoax and justify their decision in writing using their prior knowledge of science. They then complete a worksheet that teaches them how to balances forces, stepping them to the conclusion that humans can’t stand on water. Finally, the class watches part of a Mythbusters episode in which they bust this video.

Drawing from a social constructivist theory of learning, the fun and interactive nature of this 1-hour activity makes it perfect for the first day of class. It is designed for students who do not yet have a strong background in Mechanics, such as students who have not taken upper level physics in high school.

Instructional Objectives

By the end of this activity, students will be able to:

  • Calculate how much applied force (magnitude and direction) is required to fully counteract an object’s weight.
  • Explain why humans can’t run on water.
  • Draw a free body diagram to support the above explanation, following conventions.

Workflow & Materials

Workflow

Activity Workflow

View on CourseFlow
Document

Worksheet: A Learning Guide for Running on Water

Phoebe Jackson

Video Collection

Videos - Liquid Mountaineering and Mythbusters

Phoebe Jackson

Contributor's Notes

Benefits
Challenges
Tips
Benefits
  • Connects physics to students interests outside of school (especially if your course is sports oriented)
  • Acts as an ice-breaker if used early in semester
  • Does not require any advanced physics knowledge
  • Draws out common misconceptions related to weight and balancing forces.
Challenges
  • Groups must be encouraged to justify their decision. Some groups will need help from the teacher to get their words flowing. Ask them if they can think of real life examples to help explain what they are thinking. Often they will come up with the basilisk lizard or skipping stones. Then, ask them why these things are able to run (skip) on water and finally, have them write their reasoning down in full sentences.
  • Students are getting more canny about recognizing hoaxes. Last year I had zero groups decide they believed the video whereas previous years there were always a few who believed it was possible. I think this is ok, as they all still actively think about the ideas and must justify their decision.
  • Relating to the previous challenge, the video is becoming dated. My students still enjoy it but one day, this activity may need a new video and/or theme to achieve its purpose.
  • Time is always a challenge and this activity is no exception. Stick to the timeline you set for yourself or you will not have time for the important step of consolidation.
Tips
  • If using this as an ice-breaker, randomly assign the groups to allow your students to know more people in the class than just their friends.
  • Always circulate as students work and discuss. While they are deciding if the video is real or a hoax, go around and ask them to explain their choice to you. This will help them get their ideas more fully formed. But don’t give away whether they are on the “”right track.”” All justifications are valid at first.
  • Keep a close eye on the worksheets, gently pointing out places where students are incorrectly drawing free-body diagrams or making conceptual errors. Unlike the first part of this activity, the worksheet can be done incorrectly and it is worth your time to fix it as they go so that all of your students are starting from a similar point with forces and free-body-diagrams.
  • You could collect the worksheets and correct them at home afterward, but I do not do that. I just make sure that before they leave, I’ve approved one worksheet from each group.

Applied Strategies

Problem-Based Learning

Teamwork and collaboration