Friction is the force that resists the relative motion between two surfaces in contact. It is caused by the irregularities of opposing surfaces at a microscopic level. Friction causes objects to slow down and stop, allowing us to walk without slipping and hold objects. It also produces heat and wastes energy in machines. Friction can be reduced through polishing surfaces, lubrication, and using wheels and bearings. While friction wastes energy, it also enables important functions like braking and gripping objects.

1. FRICTIONAL
FORCE

2. The force of friction is the resistance to motion that is in the opposite
direction of the traveling object. That is why if you roll a ball on the
ground, it eventually stops. Friction is also the reason why you can hold
a notebook, and the reason why you do not slip when walking. The
ground and other solid surfaces can cause friction called dry friction, but
fluids (liquids and gases) like water and air can also causes frictional
forces called fluid friction. (Mercado & Dela Paz, 2016).

3. Effects of Friction
You are capable to walk on the floor due to the force exerted
by the floor adjacent to the force exerted by your feet. You are able to
push objects on a table due to friction.

4. Friction produces heat energy. When
you rub your palms against each other,
how do you feel? Friction is a nuisance.
It converts kinetic energy into heat and
wastes it. This reduces the efficiency of
engines and other machines. (Mercado & Dela
Paz, 2016).

5. Reducing Friction
Friction wastes matter as well as energy.
It causes wear in tires, soles of shoes,
and the moving parts of machinery.
Materials that are worth millions of pesos
are ruined each year by wear. Look
around your home and school for things
that have worn out because of friction.

6. Much energy in the gasoline burned in
cars is wasted by friction. Electricity is wasted
when an electric motor heats up because of
friction.
How can you reduce friction? Polishing
the surface will smooth out the irregularities
and the roughness between the surfaces,
which in turn, will reduce the coefficient of
friction that the surfaces will generate.

7. Lubricants are slippery materials that reduce friction. Lubricating a surface
with oil is another way to reduce the friction on it. Ask a mechanic or
perhaps your own father or driver to explain how a car is greased and oiled.
Ask about the spots in the car that are lubricated and how often. Sometimes,
graphite, a flaky form of carbon, is rubbed on spots where oil is liable to
collect dust. (Mercado & Dela Paz, 2016).

8. Using Rollers, Wheels, and Bearing
Have you observed your beds, sala set,
and some big appliances at home? Why
can you move them easily? What do you
think are the uses of balls and bearings
in engines?

9. An ice-cream cart can be pushed easily
because it has wheels. The bearings in the
wheels at the bicycle enable it to move
easily.

11. Life without friction
Is friction totally undesirable? Should it be
eliminated? Ask your father how the breaks
in his car work. Imagine yourself walking on
a road covered with grease. Can you walk
easily on a greased surface?
Friction plays an important role in your life.
Without friction, you cannot walk, tie your
shoelaces, pick up things, raise things, or
drive nails into boards. Friction also keeps
lids on jars. Can you imagine how life would
be without friction? (Mercado & Dela Paz, 2016).

12. Any question?

13. Direction: Analyze the following situations. Write FACT if the situation
shows how friction affects movements of objects or BLUFF if it does NOT.
____________1. Flipping a page
____________ 2. Falling of leaves from trees
____________ 3. A washing machine pushed along a floor
____________ 4. A person sliding down a slide
____________ 5. The bottom of a glass being pushed across a table
____________ 6. A paper sliding against the paper holder once released from a copy
machine
____________ 7. Jeans on your legs when putting them on
____________ 8. The bottom of a trashcan sliding against the concrete
____________ 9. Our shoes and the floor stop us from slipping.
____________ 10. The brakes and wheel help bikes and cars to slow down.
FACT
BLUFF
FACT
FACT
FACT
FACT
FACT
FACT
FACT
FACT

14. Assessment

15. Thank you. 