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Project Summary

Difficulty	2
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	No issues

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Abstract

Objective

The goal of this project is to compare friction between dry and icy surfaces by measuring slip angle and slip height.

Introduction

Friction is the resistance to motion when two objects rub together.

For example, would it be easier to ride your sled down an icy snow-covered hillside or down a rough gravel driveway? It is easier to ride your sled down the icy hillside because both the runners on your sled and the hillside are smooth and slide past one another with little resistance. The icy hillside is an example of a surface with low friction.

Riding your sled down the gravel driveway is difficult due to the rough surface of the driveway resisting the motion of the sled. The gravel driveway is an example of a surface with high friction.

Terms, Concepts and Questions to Start Background Research

• friction
• motion
• resistance
• gravity

Questions

• What is friction?
• How can friction be overcome?
• When is high friction beneficial? When is it not beneficial?
• When is low friction beneficial? When is it not beneficial?

Bibliography

• Introduction to General Physics Concepts:
  Hewitt, Paul G, 2002. "Conceptual Physics," Prentice Hall, IL.
• Simple Physics Concepts for Kids:
  Keller, R.W., 2005. "Real Science for Kids: Physics, Level 1," Albuquerque, NM: Gravitas Publications, Inc.

Materials and Equipment

• 2 2×4s cut to 0.5 m length (about 20 in)
• small plastic tub or jar with lid
• sand
• water
• freezer
• books
• metric ruler
• protractor

Experimental Procedure

1. Soak one piece of wood in water and freeze overnight.
2. Fill the plastic tub with sand and close the lid.
3. Build a ramp using several books and the piece of wood.
4. Determine the ramp height and ramp angle at which the tub of sand first slips down the ramp.
   1. Place the tub of sand onto the ramp.
   2. If it slips down the ramp, remove the tub, lower the ramp height and try again.
   3. If it does not slip, remove the tub, raise the ramp height and try again.
   4. Make your changes in height small enough so that you can accurately determine the ramp height and ramp angle just high enough to allow the tub to slip down the ramp.
5. At the angle that the tub first moves, measure the height of the book pile with the meter stick and the angle of the ramp with the protractor. Record your results.
6. Conduct the same experiment (steps 2–5) with the icy wood.
7. For any experiment, it is important to do multiple trials to assure that your results are consistent. Repeat steps 2–5 for at least three separate trials for each surface, and record your results. It will be easier to keep track of your results if you write them down in a table in your lab notebook. Here is a sample table for data collection:
   

   Sample Data Table
   Condition (name)	Trial (#)	Slip Angle (°)	Slip Height (cm)	Average Slip Angle (°)	Average Slip Height (cm)
   Dry Wood	1
   	2
   	3
   Icy Wood	1
   	2
   	3

Variations

• Conduct the same experiment with two dry surfaces—increase the friction by covering one board with sandpaper.
• Cover the surface of one piece of wood with oil or foil to decrease the friction.
• Instead of changing the surface of the wood, change the bottom of the tubs by rubbing with oil or covering with sandpaper.

• For more science project ideas in this area of science, see Physics Project Ideas.

Credits

La Né Powers

Last edit date: 2006-02-22 00:42:20

Career Focus

If you like this project, you might enjoy exploring careers in Physics.

	Mechanical Engineer Mechanical engineers are part of your everyday life, designing the spoon you used to eat your breakfast, your breakfast's packaging, the flip-top cap on your toothpaste tube, the zipper on your jacket, the car, bike, or bus you took to school, the chair you sat in, the door handle you grasped and the hinges it opened on, and the ballpoint pen you used to take your test. Virtually every object that you see around you has passed through the hands of a mechanical engineer. Consequently, their skills are in demand to design millions of different products in almost every type of industry.			Mechanical Engineering Technician You use mechanical devices every day—to zip and snap your clothing, open doors, refrigerate and cook your food, get clean water, heat your home, play music, surf the Internet, travel around, and even to brush your teeth. Virtually every object that you see around has been mechanically engineered or designed at some point, requiring the skills of mechanical engineering technicians to create drawings of the product, or to build and test models of the product to find the best design.

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