Force

Bab I. Force
FRICTION
I. Objective:
Observe magnitude of friction on a smooth, semi rough, and rough surface.
II. Equipment and Materials:

a. Dynamometer
b. Wooden block
c. Glass
d. Plywood
e. Broad covered with thick carpet.

III. Basic theory:
Friction is the force occured as the result of the direct contact between two body surfaces in the opposite direction toward the tendency of the body’s movement.
When you are running on the school yard, you will feel friction with the air that hits your body. When you drop a marble down into a fluid, for example engine oil as seen in figure 1, why is the movement of the marble in the fluids slower than in the air? Its because there is a force in the fluids (engine oil) from the opposite direction with the marble movement known as friction. ( Prasodjo, Budi ;2009 : 21&23)

Figure 1. (a) friction in air when a child is running and (b) friction occurs when a body moves in fluid.


IV. Procedures
1. Pull woden block with dynamometer on glass. Then write the force magnitude shown in dynamometer right when the wodenblock exactly move.
2. Repeat the step one to the other foundation.
3. Write all the data of activity result in the following table.
V. Observation Table
No. Surface Force (N)
1.
2.
3.

VI. Question
1. Rank those three surface based on their magnitude of force!
2. Which surfaces produces the biggest friction?
3. What is your conclution from the activity above?