Test For Friction

SCIENCE CONCEPT:

To make anything start moving a force is needed. When two pieces of wood are on top of each other, the friction is probably too strong to move the top piece of wood by laying your hand on the top piece. But if you place a safe liquid like dish soap between the two pieces the lubrication will reduce the friction and the wood will move easily.

STUDENT OBJECTIVE:

The student will explore friction in relationship to Newton's First Law of Motion. Friction is important in the First Law because when two things rub together, such as two pieces of wood rubbing together, it causes friction. Friction opposes motion and makes thing slow down. Once moving a force is needed to stop things. Friction is often the force that does this.

OVERVIEW:

In this activity, the student will take two pieces of wood and put one on the other. Then the student will lay a hand on the top piece and try to move it. The friction is probably too strong. The student will then place a safe liquid dish soap between the two pieces and see how well they move when they place their hand on the top piece of wood and move their hand in a clockwise motion.

PREPARATION TIME:

Variable

LESSON TIME:

25 minutes.

TEACHER PREP:

Gather materials for experiment. You will need two pieces of square wood about 5 inches by 5 inches, and dishwasher soap.

WORDS TO KNOW:

friction

lubrication

coats surfaces

tiny

projections

separation

cylinders

streamlining

rotating shaft

TEACHER TEXT:

We can reduce friction in machines by lubrication. Oil is put into the machine, where it coats surfaces that rub and makes them slippery. All surfaces have tiny projections that catch against each other as they rub. Without lubrication, there would be great friction, slowing and overheating the machine. The oil film separates the two surfaces so that their small rough spots do not catch. Oil film separates surfaces. Less friction produces faster motion and less heat.

Lubrication is not the only way to reduce friction in machines. Rolling is another way. Placing small steel balls or cylinders between two moving surfaces allows one surface to roll over the ground on wheels. The balls or cylinders do not rub against the surfaces as they roll, so very little friction occurs.

A ball bearing contains a set of balls between two rings. The inner ring can rotate easily while the outer ring does not move. The bearing can be used to support a rotating shaft, which is fixed to the inner ring of the bearing.

A third way of reducing friction is very important in transport, especially in aircraft. Streamlining gives the transport a shape that moves more easily through air or water. It has a pointed nose or bow and smooth sides, which do not push strongly against the air or water.

Reducing friction by streamlining an aircraft or car can give it a higher speed. Streamlining can also save fuel if speed is not increased. Many birds are streamlined so that they can swim at speed, catch prey and dive through the air or water.

Web Hosting Provided By The National Business Aviation Association.

Explore Space ... Not Drugs!
Hear what astronauts have to say about staying drug-free.
Last modified: Tue Mar 24 16:42:15 PST 1998