1. The Force Friction The Force Friction of

2. Will a paper clip and a tissue fall with the same speed and force? NO!!! The tissue floats slowly, moving from side to side. The paperclip falls straight down!

3. But if they weigh about the same, shouldn’t the force of gravity affect them the same? Newton was very troubled by this! He went all over, dropping objects to try to understand the force of gravity!

4. One day, when Newton was dropping things off the leaning tower of Pisa, he realized the answer... The force of gravity is the same everywhere! The objects fell with different speed and force because......... The force of gravity is the same everywhere!

5. ...There was another force acting on some of the objects! Newton was so surprised! (okay, maybe not THIS surprised!)

6. The other force is called Friction. Friction= a force that acts in the opposite direction of motion! Tissue 5 N 2 N The force of the friction cancelled some of the force of gravity!

7. As the tissue started to fall, it bumped into some air molecules! The air made the tissue have to move around, and slowed it down!

8. This special kind of friction is called air resistance! Paper 5 N 2 N Larger sized objects run into more air resistance, and are slowed by the friction. Small objects fall free! 5 N

9. Most friction happens when two objects touch. The more contact there is, the greater the magnitude of friction! 10 N 1 N 10 N 4 N

10. This is why round things don’t slow down as much when pushed: less touching! 8 N 1 N 8 N

11. 10 N 1 N Rougher surfaces also cause more friction because they act like lots of speed bumps! 1 N 9 N 1 N 8 N

12. This is why our skate shoes are flat with lots of ridges! The friction keeps us from sliding off our skateboards!