Friction Phenomenon

Friction Phenomenon

Increasing and Decreasing Friction

Friction Lab

• Effect of different surfaces

• Effect of weight

• Effect of rollers/wheels

Multiple Choice

By switching out surfaces in the lab, you explored the effect of surface on the amount of friction opposing the movement of the block.

Of all the surfaces, which one resulted in the most friction force when in contact with the block?

• waxed paper

• lab table top

• aluminum foil

• sandpaper

Surfaces catching and sticking causes friction.

Catch and Lock/Stuttering

Sandpaper is designed to increase catching and locking when in contact with an object.

Multiple Select

Based on your observations, which of the following are true statements?

• More force is required to move objects on rougher surfaces.

• Less force is required to move objects on rougher surfaces.

• Smoother surfaces result in increased friction.

• Smoother surfaces result in decreased friction.

Waxed paper

Using wax coats on paper creates waterproof, low-friction, non-stick surfaces.

Same idea - Using wax coats on skiis and snowboards also reduces friction.

Open Ended

Waxing objects can reduce friction. Based on what you know about the effect of surface roughness on friction, how do you think waxing does this?

Wax works partially by physically filling in bumps and ridges so surfaces catch and lock less.

Open Ended

The addition of wax works to smooth a surface by filling bumps to cause less friction (less catching and locking).

What is another way you could smooth a surface?

Sandpaper is designed to be very abrasive (lots of friction) and can physically smooth out ridges by breaking off particles from the opposite surface.

Effect of Surface Type on Friction

Surface roughness affects friction because it increases the catching and locking of particles.

More force is needed to "lift out" of deep locks and move an object.

As you added weight to the car, or doubled the blocks, it took more washers (force) to move it.

The harder the surfaces are pushed together (gravity) the more force is needed to move them.

Effect of Force/Weight on Friction

Friction force increases with weight. When an object weighs more, it requires more force to move that object than one that is lighter.

Open Ended

One portion of the lab, you were to use rollers (either bamboo skewers or straws) and also a car with wheels to move your block.

How did the addition of wheels affect the force needed to move the block?

Less force was needed to move the block. The addition of wheels dramatically decreases friction.

Effect of Wheels/Rollers on Friction

The addition of wheels or rollers to a system reduces friction dramatically.

Part of this is due to reduced surface contact.