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# Friction

Friction: Don't Slip!
Materials:
• Kinazium set
• Sphero Bolt, Mini, or other robot (if you have more than one type it will be good for comparing traction)
• Painters tape
Amount of time:
• 30 - 45 minutes
• 3rd - 7th

# Introduction

This activity introduces the physics concept of friction and traction. It teaches how different surfaces move in relationship to each other.

# Procedure

1. Watch the beginning of the video to help introduce traction to the students. Have them compare the soles of their shoes and consider which might be more sticky or more slippery.

2. Have students build a ramp with a medium slope. (We would suggest using a long ramp and the height of the ramp is in the second notch.) It will be helpful to also put a set of walls leading up to the ramp to help with robot control.

3. Next, test the ability of the robot to go over the hill, the ramp should be steep enough for the robot to struggle and or fail to go over the ramp.
4. If you are using a Sphero, now take painter's tape and put it around the middle of Sphero and add another piece 90 degrees to that tape around the opposite axis. You may need a third piece of tape around the last axis in all X, Y, Z. Test Sphero’s ability to go up the ramp, even try with each addition of tape on an axis.
5. If you have other robots, test the robots and examine whether they have enough traction to go over the ramp, if they do not, consider what modifications you might need to help. (HINT: put the painters tape on the ramp to make it less slick)

# Vocabulary

Slope: The ratio of rise over run, the height of the hill over the diagonal length of the hill(to demonstrate, use a 30/60 triangle to show a slow rise versus a steep rise depending on which side you use for the base of the triangle)

Friction: The resistance that one surface or object encounters when moving over another

Traction: Stickiness of one surface with another

Slip: When an object can’t achieve enough speed or traction

Newton: In mathematics Friction is depicted as a force N, which is named after Isaac Newton

# Assessment

Discuss the results with the students Ask why the painter's tape increases the friction. (Smooth surfaces vs rough)

Advanced Activity: Discuss how friction is a force in nature and that there are different types of friction, for example static and moving. The amount of friction an object has is defined by the coefficient of friction.

This coefficient of sliding friction is smaller which means there is less friction, than the coefficient of static friction. That’s why it is easier to slide something that’s already sliding, but to move something that is standing still, you must apply some force.