First Law of Motion: The Law of Inertia An object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same speed and in the same direction, unless acted upon by an external net force (unbalanced force)

1. FIRST LAW OF MOTION
By: Anabelle G. Montevirgen

2. Relate your experiences.
• Suppose the jeepney that you are riding suddenly stops,
what happens to you?
• Or suppose the jeepney which is iniatially at rest
suddenly moves forward, what will be your reaction?

3. Let’s Investigate!
• Objectives:
1. Understand inertia
2. Illustrate inertia
3. Understand Newton’s laws of motion
Materials
Balls (different size), glass, coins, sheet of paper,
straw.

4. • Place the glass on the table. Cover the
glass with a sheet of paper. Place a coin
on the cover. Snatch the paper cover off
the glass. Observe what happens to the
coin.

5. • Put a ball in motion and try to blow it
off of its path with a straw
Repeat this activity using balls of various
masses. Which ball was the hardest to
move off of the straight path?

6. 1) How does glass and coin activity help prove
the first law of motion?
2) Which ball was the hardest to move off of the
straight path?
3) Does inertia increase with mass?
4) Conclusion

8. Equilibrium- the net force
is equal to zero ∑F=0
If the acceleration is zero
then the forces are
balanced
Two types of equilibrium– static
equilibrium—the equilibrium of
those objects at rest
Dynamic equilibrium—the
equilibrium of those objects that
are moving with constant velocity

9. Defining Inertia
Inertia- Tendency of
a body to resist
changes in its state
of motion
The experiment conducted by Galileo
resulting to his concepts of inertia

10. • What do you
think caused the
dummy to move
forward even
after the car
stopped?
• Why has stopped
moving when the
car stopped?

11. There are several applications of the Law of
Inertia. Some are listed below. Explain how each
one is considered a manifestation of Newton’s
first law:
1. When riding on a descending elevator that
stopped suddenly, the blood rushes from your
head to your feet.
2. To tighten the head of a hammer onto the
wooden handle , you ram the bottom of the
handle against a hard surface.
3. A brick is painlessly broken over your hand when
you slam the brick with a hammer ( Caution: Do
not attempt this at home)

12. 4. To dislodge ketchup from the bottom of a ketchup
bottle, the bottle is often turned upside down, thrust
downward at a high speed, and then abruptly halted.
5. Headrests are placed in cars to prevent whiplash
injuries during rear-end collisions.
6. Seatbelts are used in order to prevent passengers
and drivers from flying off a moving vehicle due to
sudden stopping or head-on collisions.

13. Concept Micro
• First Law of Motion: The Law of Inertia
An object at rest tends to stay at rest, and an object in
motion tends to stay in motion with the same speed
and in the same direction, unless acted upon by an
external net force (unbalanced force)

14. Anabelle Montevirgen