A New Spin on Friction
A Physical Science Experiment Designed to Inquire Into Resistance
Aug 19, 2009
A new spin on friction focuses on kinetic, static, fluid, and skin friction to help students make connections with this force in other contexts, instead of only using ramps or flat surfaces when teaching this concept. Primarily, teaching friction focuses on experiments involving sliding or kinetic friction along with static friction, as students move objects over flat surfaces using a variety of materials.
However, there are two further types of friction that students need to investigate. These additional forces are called fluid friction and skin friction. These two forces are the result of objects moving through or across a liquid. This activity provides models of how to increase students understanding of friction using innovative experiment techniques.
- Skin Friction – occurs from the resistance of a fluid (liquid or gas) against the skin of the object moving through the medium.
- Fluid Friction – called drag, which refers to forces of resistance which oppose the motion of an object through a fluid (liquid or gas).
Investigation into Frictional Forces
The purpose of the following experiments is to investigate how friction opposes the motion of round objects in various mediums. This investigation also involves the use of problem solving and science process skills, along using inquiry with the scientific method.
Materials – per group
- 2 – Large Clear Containers (8 inch square) or Similar
- 1 – Stop Watch
- 1 – Ping Pong Ball
- 1 – Floating Golf Ball
- 1 – Racquet Ball
- 1 – Balance Beam Scale or Similar
- 1 – Measuring Tape or Similar
- Water
- Sea Water (water with a concentration of 3.5 percent sea salt)
- 1 mL - Vegetable Oil
- Paper Towels
- Computer Graphing Program or Graph Paper
Procedures Part One – Skin Friction
Students:
- Make prediction of which ball will spin the greatest amount time in the water and sea water.
- Measure the mass of each ball and record, using the balance beam scale.
- Measure and record the diameter of each ball using the measuring tape.
- Add water to one large clear container and sea water to the second large clear container.
- Place the ping pong ball in the container with water and spin, using the stop watch to record the time until it stops spinning (repeat three times to obtain an average).
- Place the ping pong ball in the container with sea water and spin, using the stop watch to record the time until it stops spinning (repeat three times to obtain an average).
- Repeat Steps 4 and 5 using the golf ball.
- Repeat Steps 4 and 5 using the racquet ball.
- Graph the results of this experiment.
Part One – Questions for Students
- What forces were acting on each ball as it spun around in each container?
- How do these forces act upon a swimmer?
- How about the way these forces act on a fish?
- Which ball spun the longest in water?
- Which ball spun the longest in sea water?
- Why do you think the ball that spun the longest amount of time?
- Which ball spun the least amount of time?
- Why do you think it spun the least amount of time?
- What are differences between the surfaces of the balls?
- Did actual findings from the experiment match predictions?
Students have concrete experiences with the interaction of skin and kinetic friction for each ball during this investigation.
Procedures Part Two – Fluid Friction
Students:
- Make a prediction of which ball will spin the greatest amount of time on the flat surface, with or without the vegetable oil.
- Place ping pong ball on flat surface and spin, recording the time until it stops.
- Repeat Step 1 using the golf ball and racquet ball.
- Pour the one mL of vegetable oil on the flat surface.
- Place the ping pong ball on the vegetable oil and spin, recording the time until it stops.
- Repeat Step 4 using the golf ball and racquet ball.
- Graph the results of this experiment.
Part Two – Questions for Students
- What forces were acting on each ball as it spun on the flat surface?
- What was the impact on the balls after the vegetable oil was added to the flat surface?
- Which ball spun the longest on flat surface without the oil?
- Which ball spun the longest on the surface with the oil?
- Why do you think the ball that spun the longest amount of time?
- Which ball spun the least amount of time?
- Why do you think it spun the least amount of time?
- Did actual findings from the experiment match predictions?
Students have concrete experiences with the interaction of fluid, kinetic, and static friction for each ball during this investigation.
Additional questions will emerge as students answer these and pose their own.
Making Connections Between a Science Experiment and Understanding
Students develop a greater understanding of frictional forces, because they move beyond the traditional investigation of only using ramps or flat surfaces. This hands-on concrete experience provides students with one of the best approaches to understanding all frictional forces.
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