Friction in Water

SCIENCE CONCEPT:

Newton's First Law of Motion: objects at rest remain at rest and objects in motion remain in motion unless acted upon by an outside force.

STUDENT OBJECTIVE:

The student will discover that friction is an outside force that acts upon objects to make them slow down.

OVERVIEW:

The student will use bowls of water and balls to discover that friction acts upon objects to slow them down.

PREPARATION TIME:

5 minutes.

LESSON TIME:

10 minutes.

TEACHER PREP:

Gather materials.

WORDS TO KNOW:

spin

slow down

quickly

friction

TEACHER TEXT:

Sir Isaac Newton's Second Law of Motion tells us how an object's motion changes when a force acts on it. To explain it clearly, we need to define two terms: mass and acceleration. Mass is the amount of matter or substance an object is made of. Acceleration is the change in speed (either slower or faster) with respect to time. As Newton's First Law states, an object cannot accelerate or decelerate unless force is applied to it.

Most of the motions that we find on earth involve friction. Friction is a force which occurs when two surfaces rub against one another. If you roll a ball slowly across the floor, the ball's speed decreases and eventually it stops. It stops because the friction between the ball and the floor pushes against the ball and reduces its motion.

Skin friction is a form of drag which occurs between a fluid and a solid surface. Airplanes, cars, and boats are all effected by skin friction drag. For airplanes and cars, the fluid is air while for boats, it is actually a combination of water and air. The drag produced by the water is much larger than the drag due to the air.

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Last modified: Tue Mar 24 17:19:05 PST 1998