Slip Sliding Away: Experimenting with Friction
|Time Required||Very Short (≤ 1 day)|
|Material Availability||Readily available|
|Cost||Very Low (under $20)|
AbstractAs you headed up the mountain to enjoy your last ski trip, you may have noticed a sign reading: Hazard! Icy Roads Ahead—Put On Your Chains. Putting chains on car tires increases the resistance between the tires and the road allowing the car to "grip" the road. This resistance to sliding is called friction. In this experiment, you will be investigating how to increase and decrease the friction between two surfaces.
Compare friction between dry and icy surfaces by measuring slip angle and slip height.
Cite This PageGeneral citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.
Last edit date: 2017-07-28
When driving a car down a road, the friction that allows the car to move is between the car's tires and the road. Friction is the resistance to motion when two objects rub together. Friction normally allows a car to "grip" the road. However, when the road is icy, the friction between the two surfaces decreases and this may allow the car to slip.
To understand the difference between situations where there is high friction or low friction, think about whether it would 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 icy hillside are smooth and slide past one another with little resistance. This is an example of low friction. On the other hand, riding your sled down the gravel driveway is difficult due to the rough surface of the driveway resisting the motion of the sled. This is an example of high friction.
As you can imagine, friction partly happens when the rough parts of an object catch the rough parts on another object as they rub together. The friction that occurs depends on a value called the coefficient of friction. This is a measure of how much two objects interact with each other when rubbing together, and this depends on what the material the two objects are made of. The friction that takes place also depends on the mass of the moving object (and gravity). In other words, the heavier the object, the greater the friction. All of these factors play a role in determining the friction that takes place between two rubbing objects.
In this science project, you will investigate how friction affects how well an object moves down an icy surface compared to a dry surface.
Terms and Concepts
- Coefficient of friction
- 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?
- Carr, Karen, Portland State University. (2011, October 24). Friction. Retrieved February 10, 2012, from http://www.historyforkids.org/scienceforkids/physics/machines/friction.htm
- Rader's Physics4kids.com. (n.d.). Motion Basics: Friction. Retrieved February 10, 2012 from http://www.physics4kids.com/files/motion_friction.html
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.
News Feed on This Topic
Materials and Equipment
- 2×4 wooden boards cut to 0.5 m length, or about 20 inches (2 boards are needed). Note that 2×4 wooden boards are 2 inches by 4 inches.
- Small plastic tub or jar with lid
- Metric ruler
- Lab notebook
Slip Sliding Away: Experimenting with Friction
- Soak one piece of wood in water and freeze overnight.
- Fill the plastic tub with sand and close the lid.
- Build a ramp using several books and the piece of wood.
- Determine the ramp height and ramp angle at which the tub of sand first slips down the ramp.
- Place the tub of sand onto the ramp.
- If it slips down the ramp, remove the tub, lower the ramp height and try again.
- If it does not slip, remove the tub, raise the ramp height and try again.
- 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.
- At the angle that the tub first moves, measure the height of the book pile with the meter stick (in centimeters [cm]) and the angle of the ramp with the protractor (in degrees [°]). Record your results.
- Conduct the same experiment (steps 2–5) with the icy wood.
- 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 your lab notebook in a data table like Table 1 below.
- Calculate the average slip angle and the average slip height for each condition (the dry wood and the icy wood). Record your results in your data table.
- When you are done testing, look at your results and try to draw some conclusions. How does the friction compare between the dry and icy surfaces based on your average slip angles and average slip heights?
|Sample Data Table|
|Average Slip Angle
|Average Slip Height
If you like this project, you might enjoy exploring these related careers:
Mechanical EngineerMechanical 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. Read more
Mechanical Engineering TechnicianYou 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. Read more
- Conduct the same experiment with two dry wooden boards and increase the friction of one of the boards by covering it with sandpaper. How does the increased friction on the board affect how well the tub slides down it?
- Cover the surface of one piece of wood with oil or foil to decrease the friction. How does this change how the tub slides down the wood compared to sliding down wood that is not covered with oil or foil?
- Instead of changing the surface of the wood, you can try changing the bottom of the tub by rubbing it with oil or covering it with sandpaper. How does this change how well the tub slides down the ramp compared to a tub that has not been changed?
- If you want an advanced challenge, you can try to calculate the angle of the ramp. If you know the height of the ramp and the length of the ramp, you do not actually need a protractor to figure out the angle of the ramp. All you need is to do some math. The equation used to solve the angle of the ramp is sin(theta)=opposite/hypotenuse. "Theta" is the angle, "opposite" is the ramp height, and "hypotenuse" is the ramp length. Find out more about how to do this calculation at Finding an Angle in a Right Angled Triangle from Math is Fun Advanced. Does the calculated angle match the one you measured with your protractor?
Ask an ExpertThe Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
Ask an Expert
News Feed on This Topic
Looking for more science fun?
Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.Find an Activity