Daily Science1. If a book is sitting on a desk would it be a

balanced force or unbalanced force? Using arrows, show what forces are acting on the book.

2.How would you make the book become unbalanced if it’s balanced.

Scenarios

What are the similarities between each scenario:

•You sitting in a chair

•Puck gliding across the rink

•Brakes stopping a car

•Football players colliding

•Tires screeching across the pavement

•Riding your bike

•Surfing on some killer waves

What is friction?

• Friction is a force that two surfaces exert on each other when they rub against each other.

• What two factors do you think affect friction?

Two factors that affect friction.

• The first factor is how hard the surfaces push together.

• Ex. Rubbing your hands together, the harder you rub your hands the warmer they get.

• The second factor is the types of surfaces involved.

• Would you rather rub your face with sand paper or wax paper?

Types of Friction

• There are four types of friction:

1. Static Friction

2. Sliding Friction

3. Rolling Friction

4. Fluid Friction

Static Friction

• Static Friction is when friction is acting on objects that aren’t moving.

• What could be some examples of this?

• Example: desk not moving, standing still, pencil laying on desk.

• The objects aren’t moving because of friction.

Sliding Friction

• Sliding Friction occurs when two solid surfaces slide over each other.

• How can this be useful?

• Spreading sand on ice for more traction, using your brakes on your bike to stop.

• How can this not be useful?

• Slipping and falling on ice, falling off bike and skinning your knee.

Rolling Friction

• Rolling friction is when objects roll across something. This provides rolling friction.

• What are some examples of rolling friction?

• Skateboard, rollerblades

• What do scientist use to reduce the amount of friction in wheels?

• They use ball bearings.

Fluid Friction

• Fluid friction occurs when a solid object moves through a fluid.

• Some types of fluids are water, air, and oil.

• What are some examples of fluid friction?

• Surfing

• How is riding a bike an example of fluid friction.

• A cyclists cuts through the air.