Friction

Friction Ff

The symbol for friction is ________

The unit for friction is _____________

①

What is friction?

Friction is the __________ that ____________ the __________between objects.

②

Your teacher (or a volunteer) is going to push a book across the table.

Predict what is going to happen to the motion of the book when the person stops pushing it.

Predict③

Will it keep moving at the same speed in the same direction forever?

Will it slow down and come to a stop?

Will it speed up and crash through the wall?

Observe

What did you observe happen to the book?

④

Explain

Why do you think the book moved the way it did after the person stopped pushing it?

⑤

Friction

If the book is pulled at a slow, __________________, the forces on the

book

are _________________.

⑥

The Net Force is _________.

Arrows are often used to show forces. The diagram below shows a book being pulled to the right at a slow, constant speed.

Draw and label a second arrow to show the force of friction that acts on the book (make sure it points in the correct

direction and is the correct size). .

Friction points in the _____________ direction as the pulling force.

The friction force is _________ size as the pulling force.

⑧If the book is pulled at a slow constant speed, the ________________ should be the __________ as the ____________________.

The teacher (or a volunteer) will pull the book at a slow, constant speed across the table with a spring scale. The force that is read off the spring scale is the same size as the force of friction.

 Force of friction on the book = Ff = _________ N  

Does FRICTION depend on the TYPE OF SURFACE?

With a partner, take a spring scale and an object and try pulling the object at a slow, constant speed across several surfaces.

⑨

Does FRICTION depend on WEIGHT?

With your partner, take a spring sale and a set of masses

First weigh the mass by hanging it from a spring scale.

Next pull the mass along the table at a slow and constant speed.

Record the force required to overcome the force of friction.

⑩

The force of friction when objects are not yet sliding past one another is called ___________ FRICTION.

Your teacher is going to try to push an object, but it won’t move.

⑪

The force of friction when objects are sliding past one another is

called ______________FRICTION.

Your teacher is going to push the same object again, but this

time it moves.

⑫

Friction can __________________________________ ⑬