Newton’s Laws at an All-Season Snow Hill

In the video portion students can see tubers sliding down the Snowflex® hill, experiencing different types of motion, velocity, and acceleration.

Teachers can consider introducing free body diagrams, forces on an incline, and components of gravity (weight) that act on the tuber. Explain that the x-component of the force is the unbalanced force if the tubers are accelerating down the hill (in the direction of the force). You can also introduce friction as being dependent on the y-component of gravity (weight), where the f_f= η_kF_N, where F_N=mgcosθ.

There are many hills in Iowa, formed by glacier deposits 14,000-15,000 years ago, or by erosion due to glacial melting, which has led to several skiing and tubing sites, both formal and informal, across the state of Iowa. Force, velocity, acceleration and friction are all experienced while tubing on these hills.

Des Moines

Iowa Core Standard

HS-PS2-1

Analyze data to support the claim that Newton's second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration

Driving Question

What factors affect the motion of the tube down the SnowFlex® hill?

Probing Questions

Before the tubers start down the hill, what must happen for the tubes to move down the hill?
As you look at the video, how can you describe the motion of the tubers as they come down the hill?
Why are they accelerating? What unbalanced force is on them?
What factors would lead to a faster/slower speed at the bottom of the hill?
What is the coefficient of friction of the hill, based on the data collected?
How can you model the motion of the tuber down the hill?

Classroom Suggestions

Students could:

Use an inclined plane at different angles and with different lubricants on the surface to determine factors affecting final speed and acceleration.
Brainstorm ways to represent different forces on objects (free body diagrams).
Visit a snow hill such as the one shown and take time data at 100-foot intervals to graph and show acceleration. Use different push forces at the top of the hill to determine the effect on acceleration and final velocity. Alter the mass (single vs. multiple tubers) and collect data to determine if mass has an impact on final velocity and acceleration.
Use data to calculate the coefficient of friction between the hill and the bottom of the tube.
Determine how you could calculate the force of friction if the angle and the coefficient of kinetic friction (k) are known (Note: the angle of the Snowflex® hill is 16° on the steep slopes, and η for plastic on plastic is 0.1)

Resources

Veritasium | What is a Force?: This is a video that asks normal people what a force is. You can pause at 1:16 for a discussion of the Nature of Science and the difference between a theory in science versus the colloquial use of the word. At the end of the video, pause at 3:20 and see if anyone can identify the upward force, or you can wait until the end of the video to have this discussion.
Flexbooks | Newton’s Second Law: This guide provides an introduction to Newton’s second law.
Khan Academy | Newton's first and second laws: This resource provides readings and lesson checks.
Open Stax | Drawing Free Body Diagrams: This lesson covers rules for drawing a free-body diagram and constructing free-body diagrams for different situations.
Friction on an Inclined Plane Lab: Investigating Effects of Weight & Various Surface Coatings: This teacher-created lab investigates the effect of weight and type of lubricant on the Snowflex® hill in preparation for a field trip to the site.
Lab - Newton's 2nd Law on the Snowflex® Hill: This teacher-created lab investigates the effect of different forces and masses on acceleration down the Snowflex® hill. It is designed for students to experience the hill while taking data to bring back to the classroom to analyze.
Sleepy Hollow | Hills, Thrills and Newton's Laws - 5E NGSS Lesson: This teacher-created plan was developed for Sleepy Hollow.

Contributors

Submitted by Rose Davila-Gay as part of the Iowa STEM Teacher Externship program.