# Rolling Friction

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#### Updated on Feb 06, 2012

Grade Level: 6th - 8th; Type: Physical Science

Students will examine how tire treads on a bicycle affect rolling frictional force.

• How does rolling friction differ from sliding friction?
• How do tire treads affect rolling friction?

Tires are the only objects separating the vehicle from the road whether it be driving a car or riding a bicycle. That is why it is important to maintain proper tire tread depth and pressure in order to balance the amount of traction and speed. The surface of a tire affects rolling friction, the frictional force between a round object such as a tire or a ball over a surface. Some tires are smooth while others have large grooves, or treads. Race car tires are smooth without treads in order to increase speed compared to an all terrain vehicle that has larger, treaded tires to increase traction while driving off road. In this experiment students will examine the affects of tire treads on rolling friction.

• Bicycle with two sets of tires (street and all terrain)
• Street tires
• Mountain/trail tires
• Air Pump
• Stopwatch
1. Map a bicycle route that includes traveling on paved roads, gravel/dirt, and grassy surfaces.
2. Measure the amount of time it takes to complete sections of the route with the street tires. Be sure the tires are properly inflated according to the tire manufacturer. Repeat two more times and record the time.
3. Start and stop the stopwatch at the same points on the route for each trial. Record the times for each section: paved road, gravel/dirt, and grass.
 Paved Road Gravel/Dirt Grass Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3 Street 5:33 5:21 4:57 3:22 3:14 3:52 3:55 4:02 4:01 All Terrain 6:33 6:00 5:58 3:14 3:11 3:02 3:14 3:11 3:02

Times recorded in minutes.

1. Repeat steps 2 & 3 with the all terrain tires.
2. Take an average of the your times for both street and all terrain tires. Calculate total route time.
3. Which tire was the fastest?
4. Which tire performed the fastest on paved roads?
5. Which tire made it easy to ride through gravel/dirt and grassy paths?
6. How did tire treads affect speed, traction, and required force while peddling on each surface?

Terms/Concepts: Friction; Rolling friction; Force; Resistance

References:

Melissa Bautista is a research scientist, freelance editor, and writer, with a focus in Neuroscience. She believes in establishing solid foundations in education through experience, creativity, and collaboration. She is fascinated by pedagogy and the concept of learning through living.