2. When you dribble a ball, you
hold the ball first and then
apply a downward force on it.
The ball bounces on the floor
and then goes back to your
hand repeatedly.
When you dribble the ball, the
force that you exert on it is
push.
3. It shows a girl stretching a
bow.
As the girl stretches the bow,
she exerts a pull on it.
5. o Can you feel the force exerted
by the book due to its weight?
o Although you cannot see the
force, you can feel its effect.
6. What can force do?
- causes an object or a body at rest to move.
- causes the moving object or body to stop, change its
direction of motion, or gain or lose speed.
Ex:
Get a ball and roll it on the floor. Make its directions as it
moves and then make stop moving.
Do you realize that you have just applied force to the ball?
What type of force acted on the ball?
How did that force affect the movement of the ball?
8. TWO TYPES OF FORCE:
– type of force results from
direct contact between two
surfaces.
• Ex:
• Catching ball, striking a match,
scrubbing the floor, and
hammering a nail.
• Friction
– type of force that does not
involve direct contact between
objects.
- act in a distance.
• Ex:
• gravity
9. FRICTIONAL FORCE/FRICTION
- contact force that is present whenever the surfaces of two materials are in
contact with each other.
- It resists the movement of the material over another.
- Attraction of the particles of two materials when their bumps and hollows
rub against each other.
- Ex:
- Wheels of the vehicles rolling on the road (friction causes the vehicle to run slowly), the
tire of the vehicle and the road are two surfaces that tub together, bumps and hollows
cause resistance in the movement of the surfaces over each other. The irregularities on
the surface can be more obviously seen on rough surfaces than on smooth surfaces.
- the soles of the shoes touching the ground as you walk
10. • Amount of friction affects the motion of an object.
• Try rolling a ball on the smooth surface
• Do the same in the rough surface
• There is difference on the motions of ball
• Smooth surface (newly polished floor) –
produces less friction which enables objects to
move fast.
• rough surface (bumpy road) – produces
greater friction causing the object to move
slowly.
• Running vehicles in the expressway.
• They travel on the expressway faster than on
rocky rough road.
• They can speed up from a minimum of 60 kph
up to 100 kph because of the smooth road,
there are no holes and humps that slow down
their speed.
• If travel in a rocky road, they would not be able
to run with those speeds.
11. • Can walk faster in a smooth surface than rough one
• Amount of friction depends upon on the smoothness of the two surfaces
touching each other.
• If the soles of the shoes have deep canals and the ground is not slippery,
you can walk straight without falling because of the resistance caused by
high friction
• However, if the soles of the shoes re already smooth or worn out, ten you
may slide down the ground because less friction resist the movement.
• Basketball players usually wear rubber shoes with deep canals on the soles
to avoid sliding down while running the court. They need to increase
friction to prevent accident.
12. • Friction also exists in the air.
• Get two pieces of paper and then crumple one of them.
• Hold the pieces of paper, with one on each hand.
• Drop both pieces from the same height at the same time.
• Observe which piece of paper reaches the floor first.
• Crumpled paper falls down faster. Because it has less exposed surface. It
produces less friction with air as it falls down
• On the other hand, because the exposed surface of the paper that was
not crumpled is greater, there is greater friction with the air. Thus, paper
falls down more slowly, proving that there is also friction in air. This type
of friction depends on the surface area of the objects that is exposed in
the air.
13. • There is also friction in water.
• Can be observed when watering plants in a garden using a hose.
• Water moves through the hose easily because of low viscosity (ability of liquid to resist
flow). Thus, water produces less friction with the lining of the hose.
• Other fluids like grease, which has high viscosity, would have a harder time moving
through the hose because they produce higher friction.
• Friction causes water resistance, which slows down swimmers and boats travelling through
the water.
15. Static Friction
- friction between two objects in contact
that are not moving.
- Ex:
- Pencil lying on the table
- Book on the shelf
- Bag resting on a chair
- There are two surfaces rubbing each
other in each situation – the pencil and
the table, the books and the shelf, and
the bag and the chair – there is static
friction between this pair.
- Objects remain at rest because of the
balanced forces they exert toward each
other;.
16. Sliding Friction
- friction that occurs when the bumps and
hollows on the surfaces of two materials
resist against each other.
- There is sliding friction when two solid
surfaces slide over each other.
- It is produced in instances such as
pushing and pulling the mouse the
mouse of your computer and pushing a
flatiron on the cloth during ironing.
- Ex:
- sliding friction when you play on a
slide in the playground
- go through the slides in swimming
pools
17. Rolling Friction
- force between a wheel or a roller and the
surface which it is in contact with.
- Ex:
- Wheels on the road
- Bowling balls rolling on the alley
- Wheels of the skateboard played by
the young boys in a park
18. EFFECTS OF FRICTION
walk steadily
In physical education, wearing rubber-soled shoes increase friction and prevent
from slipping off the smooth surface if the gymnasium.
Can walk firmly with a leather shoes on rough surface
helps stopping moving objects, ex: brakes use friction to slow down moving
vehicles because of the rolling resistance against the wheels. If you roll a ball in a
flat area, it will stop eventually even without bumping on any object because
friction exists between the ball and the ground.
Helps to unscrew the tops or lids of bottles, jars, and cans. Twisting the tops of the
jars to open them creates sliding friction between the surface if the top and your
hands.
19. EFFECTS OF FRICTION
In wood fixtures, static friction holds nails and screws in place.
Also used to make things smoother, as when sanding wood in pieces of furniture.
When one scrubs a rough furniture with sandpaper, its surface becomes smooth
because friction is present on the surfaces of the sandpaper and the wood as they are
rubbed together.
Helps to identify objects and determine how these objects should be handled. The
texture will tell which should be handled tightly (slippery) and not so tight (rough).
Friction is present when you rub the hands together. The friction produces heat,
making your hands feel hot.
Rubbing sticks together, will produce heat and if they are rubbed for long enough, the
heat produced may be sufficient to cause a spark and start a fire.
20. EFFECTS OF FRICTION
It can be harmful too.
Wears away things, the tires of vehicles, as well as the shoes and clothes you wear,
are worn away by friction.
Moving and rubbing machines parts also wear away gradually because of friction.
Can hurt yourself or develop a bruise whenever your skin hits the rough surface
against it. It is gradually difficult for soft skin to resist a hard and rough surface.
Makes work harder at times, such as when moving a heavy appliance to another
place. Additional force is required to overcome friction.
21. WAYS TO REDUCE OR INCREASE
FRICTION
Lesser or greater friction may be useful or harmful at times.
Learning certain methods of reducing or increasing friction is necessary.
Using lubricants - substance placed between surfaces to fill up the unevenness
and provide a thin film between the parts that rub together.
Lubricants reduces the friction between two rubbing surfaces.
Ex:
water spilled on the floor makes the floor slippery as you walk and step on
it.
Soaps help you scrub your skin easily.
Grease and oil lubricate motor parts for vehicles to run smoothly.
22.
23. WAYS TO REDUCE OR INCREASE
FRICTION
Rollers, wheels, or ball bearings
change sliding friction to rolling
friction. These objects also reduce
friction. Transferring heavy loads to
another place becomes easier when
one uses rollers or wheels.
24. WAYS TO REDUCE OR INCREASE
FRICTION
Friction in slippery surfaces needs to be increased.
Speeding cars and trucks have to be slowed down using friction to
avoid accidents from happening.
Roads are made rough and new tires have deep treads to create greater
friction.
Rubber-soled shoes with treads are better used when playing basketball
in a gymnasium so no one can prevent slipping and other-related
accidents.
25. SAFETY CONCERNS ON FRICTION
• You should practice safety measures to avoid accidents on situations involving
friction. Here are some safety measures to follow:
1. When water, oil, or other liquids spill on the floor, wipe off the liquid so you can
avoid sliding on the floor. If you see spilled water, oil, and other lubricants on
your way, avoid stepping on them. These lubricants make the pavement slippery
and can cause accidents.
2. When walking, be watchful of slippery pavements or very rough roads. Ensure
that you wear the right footwear that may help you avoid any accident. You can
do the same when playing games or doing other physical activities.
26. SAFETY CONCERNS ON FRICTION
3. When riding in a moving vehicle, be alert and hold tightly to a handrail or
anything that would help you avoid being hurt in case the driver suddenly steps on
the brakes. When a vehicle suddenly stops, your body suddenly moves forward,
which may cause you to hit any object that might hurt you.
