Predict the amount of friction different surfaces will create with this SciGirls activity. Friction is a force that resists motion when two objects are in contact. If you look closely at the microscopic surfaces of all objects, there are tiny bumps and ridges. When you try to slide one object over another using just a small amount of force, the object won't move since those tiny bumps and ridges catch onto another. This is called static friction. If you apply a little more force, the object will "break free" and slide, although you still need to apply force to keep the object in motion.
Visit pbskids.org/scigirls for more videos and projects.