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Physics
How can you decrease the force of friction?

● by oiling the contact between the surfaces

● by smoothing rough surfaces, polishing or grinding them
● by turning sliding friction to rolling friction

How can you increase the force of friction?
textbooks nis edu kz
● Vehicle tyres can be made with more grooves.

● Sand can be scattered across roads to obtain a rough surface.

● The force pressing an object down can be increased, i.e. a load is
Why do we place ball bearings
applied to the object. between moving parts?

How can you calculate the force of friction?
The force of friction can be calculated using the following equation:

F = μ ∙ N
Tp
where μ = coefficient of friction
This coefficient mostly depends on the types of surfaces in contact
with each other. In general, static friction coefficients are greater than
sliding friction for the same two surfaces. So, usually, it takes a lot more
force to make an object move than to keep it moving once it has N
already started.

and N = normal force

This is the force that a surface exerts on an object placed on it. It always F fr
acts perpendicular to the surface.

INV In this investigation you will change the type of surface in contact
with your object and compare the magnitudes of sliding friction force
required to move it across different surfaces. Repeat your experiment at
least three times for each surface to ensure the repeatability of your
measurements. Using the equation above, determine the coefficient of
sliding friction.

OVER TO YOU!

1. Describe the key features of the force of friction.

2. Think about:

a) catching a wet and muddy ball
b) using soap to remove a tight ring

c) roller-skating

Between which surfaces does friction occur? Is this friction useful, or not useful?
Explain why.

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