1. Friction Formulate at least 4 important facts about friction Objective 2 vocabulary: friction resistancemagnitude staticsliding frictionstatic friction rolling friction

2. Objective 2 Definitions:   Friction -a force that resists motion when 2 objects are touching / the resistance force between 2 objects that are ‘touching’   Resistance – opposition by a force   Magnitude – the size of something, the strength of a force   Sliding friction - the friction force that resists the motion of an object moving or sliding across a surface   Static friction - the friction force that resists the motion between 2 surfaces that are not moving. (static means unchanging)   Rolling friction - the friction force that resists the motion of an object rolling across a surface

3. Important points to know about Friction   occurs when two objects come into close contact   always acts to slow down the motion of objects   The direction of the friction force is always opposite the motion of the object   caused by differences in the microscopic surfaces; the molecules in the two materials attract each other (this is called adhesion). When you slide one object past another you need to break these bonds   changes energy of motion into heat energy

4. Friction Force  Rolling, sliding & static friction - what is the difference?  Draw & share an example of each that includes a force diagram.

5. Lab report discussion: Hypothesis writing   What is a hypothesis?   Why is it important to form a hypothesis before you start an experiment?   What are the parts of a hypothesis?   What makes a good hypothesis? Make hypothesis based on the Investigation question: Which surface will produce more rolling friction with a marble: plastic, carpet or tape?