Kinds of Friction A moving object is affected by friction. However, the amount of friction may vary depending on the type of surface the object gets in contact with. Rolling Friction When an object rolls over a surface , rolling friction is produced. One of the most common examples of rolling friction is the movement of motor vehicle tires on the road , a process that generates heat and sound as by-products. Rolling friction is easier to overcome than sliding friction for similar materials. This type of friction is important to engineers who design certain products. For example, skates, skateboards, and bicycles need wheels that move freely. Sliding Friction Sliding friction occurs when two solid surfaces slide over each other. Sliding friction can be useful. For example, you can spread sand on an icy path to improve your footing. Ballet dancers apply a sticky powder to the soles of their ballet slippers so they won’t slip on the dance floor. And when you stop a bicycle with hand brakes, rubber pads slide against the tire surfaces, causing the wheels to slow and eventually stop. On the other hand, sliding friction is a problem if you fall off your bike and skin your knee! Fluid Friction Fluids, such as water, oil, or air, are materials that flow easily. Fluid friction occurs when a solid object moves through a fluid. Like rolling friction, fluid friction is easier to overcome than sliding friction. Static Friction The friction that acts on objects that are not moving is called static friction. Because of static friction, you must use extra force to start the motion of stationary objects. For example, think about what happens when you try to push a heavy desk across a floor. If you push on the desk with a force less than the force of static friction between the desk and the floor, the desk will not move. To make the desk move, you must exert a force greater than the force of static friction.

1. Infer how friction and gravity affect movements of different objects.
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6. Friction positively affects the car
movement. For instance, without
friction, your car cannot move i.e. the
tires cannot push against the surface
(ground) to move the car and thereby
brakes cannot stop the car.
On the other hand, it can cause
problems too. Consider this example.
Friction between any engine parts
only increases the temperature and
thus causes engine parts to break
down; therefore, a coolant is added to
keep the temperature normal.
Friction Is Both Harmful And Helpful

7. As the sliding object slows down, most of the amount of
energy is transformed into heat. The friction converts
ordered energy into thermal energy or heat. For example,
in match lighting, the glass powder helps in creating
friction that’s needed for igniting flammable compounds at
the time of striking process.
Friction Often Heats Things Up

8. There’s A Strong Connection
Between Friction And Energy
Another interesting friction fact
that you might know is that
friction has a lot to do with
energy. If the two objects are
rubbing each other and one is
sliding down, it means the
objects are losing the energy.
The energy released is not at all
real and is rather kinetic energy.

16. What is a Force?
•In science, a force is a push or a pull.
•All forces have two properties:
•Direction and Size
•A newton (N) is the unit that describes
the size of a force.

17. What Causes Friction?
• Friction is the force that opposes the motion between two
surfaces that touch.
• The surface of any object is rough.
• Even an object that feels smooth is covered with tiny hills
and valleys.
• The contact between the hills of valleys of two surfaces
causes them to stick, resulting in friction.

18. •The amount of friction depends on:
•Roughness of the surfaces
•Force pushing the surfaces together
What Causes Friction?

19. The Causes of Friction
In general, smooth surfaces produce less
friction than rough surfaces.
The strength of the force of friction depends
on two factors:
* How hard the surfaces push together
* The types of surfaces involved
https://www.youtube.com/watch?v=ybpFEB6Mt88

20. Friction also increases if
surfaces push hard against
each other.
If you rub your hands
together forcefully, there is
more friction than if you rub
your hands together lightly.

21. Friction acts in a direction
opposite to the direction of
the object’s motion.
Without friction, a moving
object might not stop until it
strikes another object.

22. • Kinetic friction occurs when force is applied to an
object and the object moves.
• Examples:
Sliding Friction: pushing an object across a surface
Rolling Friction: between wheels and a surface
Fluid Friction: opposes the motion of objects traveling
through a fluid (air or water)
Types of Friction

23. •Static friction occurs when force applied
to an object does not cause the object to
move.
Types of Friction

24. Sliding Friction
Sliding friction occurs when two solid surfaces
slide over each other.
Sliding friction can be useful.
For example, you can spread sand on an icy
path to improve your footing.
Ballet dancers apply a sticky powder to the
soles of their ballet slippers so they won’t slip
on the dance floor.
And when you stop a bicycle with hand brakes,
rubber pads slide against the tire surfaces,
causing the wheels to slow and eventually stop.
On the other hand, sliding friction is a problem
if you fall off your bike and skin your knee!

25. Rolling Friction
When an object rolls across a surface,
rolling friction occurs.
Rolling friction is easier to overcome
than sliding friction for similar
materials.
This type of friction is important to
engineers who design certain products.
For example, skates, skateboards, and
bicycles need wheels that move freely.
https://www.youtube.com/watch?v=HRe90ySP38U

26. • So engineers use ball bearings to
reduce the friction between the
wheels and the rest of the
product.
• These ball bearings are small,
smooth steel balls that reduce
friction by rolling between
moving parts.

27. Ball Bearings are a type of
rolling-element bearing that
uses balls to maintain the
separation between the moving
parts of the bearing.

28. Fluid Friction
Fluids, such as water, oil, or air,
are materials that flow easily.
Fluid friction occurs when a solid
object moves through a fluid.
Like rolling friction, fluid friction is
easier to overcome than sliding
friction.
https://www.youtube.com/watch?v=ZjlBlUvqnPo

29. This is why the parts of machines that
must slide over each other are often
bathed in oil or lubricants.
In this way, the solid parts move
through the fluid instead of sliding
against each other.
When you ride a bike, fluid friction
occurs between you and the air.
Cyclists often wear streamlined
helmets and specially designed
clothing to reduce fluid friction.

30. It is a substance,
such as oil or grease,
used for minimizing
friction, especially in
an engine or
component.

31. • To reduce the amount of friction, apply a lubricant between
two surfaces.
• Motor oil, wax, and grease are examples.
• Friction can also be reduced by rolling, rather than pushing,
an object.
Affecting Friction

32. •Friction increases as surfaces are made
rougher.
•Friction increases when the force
between two objects is increased.
Affecting Friction