The Force of Friction

The Force of Friction

Goal: To determine the cause and effect of friction.

Materials: textbook, string, scissors, sandpaper, masonite board, (3) dowels,

Spring-scale.

Procedure: Part 1 (Static Friction-smooth surface 1 book)

Weigh the textbook with the spring scale as shown in Figure 35.

Record the weight, in Newtons, in the space above Data Table 1.

Place the masonite board on the lab table with the smooth side up.

Place the textbook with spring scale attached on the board as shown

in Figure 36.

Apply a steadily increasing pull to the spring scale until the book just starts to move. Record the force in Newtons on Data Table 1.

Part 2 (Sliding Friction-smooth surface 1 book)

This time pull on the spring scale until the book is moving at a constant speed (you may need to practice this several times).

Record the force in Newtons on Data Table 1.

How does the static force compare to the sliding force? How do you explain this?

Part 3 (Static and Sliding Friction-rough surface-1 book)

Turn the masonite board over and notice the rough sandpaper.

Repeat Parts 1 & 2 using 1 book and record the force in Newtons on Data Table 1.

How do the forces needed to move the books on smooth and rough surfaces compare? How do you explain this?

Part 4 (Static and Sliding Friction-rough surface-2 books)

Still using the sandpaper side of the masonite board, repeat Part 3 except this time use 2 books instead of 1. Record the force in Newtons on Data Table 1.

How does increased weight affect the force needed to move an object?

Part 5 (Rolling Friction-rough surface-2 books)

Place the dowels under the 2 books on the sandpaper side of the masonite board.

Record the force in Newtons on Data Table 1 needed to move 2 books.

How do the values for sliding and rolling friction compare? How do you explain this?

Weight of the book in Newtons: ______

Data Table

Static friction-smooth surface (1 book) -

Sliding friction-smooth surface (1 book) -

Static friction-rough surface (1 book) -

Sliding friction-rough surface (1 book) -

Static friction-rough surface (2 books) -

Sliding friction-rough surface (2 books) -

Rolling friction-rough surface (2 books) -

On separate paper: (put your name on this paper for an individual grade)

Write 1 paragraph suggesting 2 ways you could reduce friction between 2 surfaces.