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Practice 7. Factors influencing friction solutions

STUDY OF THE FRICTION FORCE

Objective.

study the characteristics of the friction force with
surfaces. See whether or not depends on the contact surface,
weight and / or the characteristics of the materials that compose
.

Material.

- Dynamometer.

- Smooth surfaces of different materials.

- wooden blocks of different shapes.

theoretical basis

The frictional force is a force that always opposes motion
. In this case we study the frictional force between surfaces
. The friction force depends on the press a
body against another and the surface characteristics of contact
. The force that makes the object on the ground in a horizontal plane
equals weight in magnitude and opposite direction. In an inclined plane
this force is equal to P _n (
vertical component of weight). Normal is called ( N ) when
perpendicular to the surface. The other factor upon which the frictional force
is the coefficient of friction μ ,
which is determined by the characteristics
of surfaces and its value is experimentally since
depends on many factors such as roughness,
type of materials, surface defects ...

therefore the friction force is expressed by: Fr = μ • N
(Newton)

Notes μ is dimensionless.

operating method

1. 
   Put the piece of wood supported by more
   face on a given surface area.
   then hooked the dynamometer to taco and put it horizontal.
   Then we always pulling horizontally
   dynamometer seeing what mark when it begins to move the whole
   . Once you start moving, keep trying to pull
   movement speed is uniform (v = constant) and we scored
   marking the dynamometer. Make 3
   measures and calculate the mean value.

   
   

2. 
   repeat the same process with the lower part of the taco
   surface.

   
   

3. 
   repeat points 1 and 2 ° but
   other contact surfaces.

   
   

4. 
   then weighs the wooden block (the dynamometer
   you better). With the calculated weight know what it is Normal (N).
   then calculates for each measure the value of μ.

   
   

calculations and results and conclusions.

With the measurements obtained complete the following table:

Cara taco	M easure 1 (N)	M easure 2 (N)	M easure 3 (N)	M easure 4 (N)	Average	Normal (N)	coefficient μ
Mayor
Menor

issues and conclusions.

1. 
   Does it depend on the friction force of the contact surface
   ? Explain it.

   
   

2. 
   If the object moves faster, keeping constant
   during the journey, "will depend somewhat
   friction force being higher, lower or equal ?

   
   

3. 
   By changing the type of surface contact, how the force varies
   friction while the block is the same? Why
   what?

   
   

4. 
   If aumentásemos body mass, how
   adjust the force of friction?