Three laws of motion 1

1. Three Laws of MotionThree Laws of Motion

2. NEWTON’S
THREE LAWS
OF MOTION

3. NEWTON’S FIRST LAWNEWTON’S FIRST LAW
A BODY AT REST REMAINS
AT REST AND A BODY IN
MOTION REMAINS IN
UNIFORM MOTION IN A
STRAIGHT LINE UNLESS
ACTED ON BY AN EXTERNAL
UNBALANCED FORCE

4. Newton’s First Law ExplainedNewton’s First Law Explained
Experience tells us that a
stationary object remains at
rest unless acted on by some
outside force. We know that
forces are necessary to cause
anything to move if it is
originally at rest.

5. Less obvious is the fact that an object in
motion will continue in motion until an
outside force changes the motion. For
example, a rolling ball slows down until it
stops rolling because of its interaction with
the floor, called friction, between the floor
and the ball. The ball will roll longer and
farther in a smooth surface than in a rough
one. This leads to the idea that if the surface
is frictionless the ball will move forever.
These ideas are part of Newton’s first law.

6. NEWTON’S SECOND LAWNEWTON’S SECOND LAW
The acceleration a of an object
in the direction of a resultant
force F, is directly proportional
to the magnitude of the force
and inversely proportional to the
mass m

7. Answer this to illustrate the Answer this to illustrate the
first law of motion.first law of motion.
In Enchanted In Enchanted
kingdom, one of the kingdom, one of the
rides was Jungle rides was Jungle
Log Jam. During the Log Jam. During the
descent of the car descent of the car
from the top of the from the top of the
rail, why did you rail, why did you
pitch forward when pitch forward when
the car slowed the car slowed
down?down?

8. Newton’s Second Law Explained!Newton’s Second Law Explained!
The Law of Acceleration:
Experience tells us that larger and
larger resultant forces on the same
object will result in greater and
greater changes in the velocity of
the object.
F 2F
a

2a

9. Furthermore:Furthermore:
If we keep the resultant force constant and
apply it to greater and greater masses, the
change in velocity decreases. The change
in velocity per init time is defined as its
acceleration a. He demonstrated the direct
relationship between the applied force and
the resulting acceleration. He showed that
the acceleration decreased proportionally
with the inertia or mass of the object.

a = — or F = ma

F
m

10. m
2m
3m
F
F
F
a
½ a
CONSTANT FORCE INCREASING MASS
RESULTS IN DECREASING VELOCITY
?
1.
2.
3.
What would be the
acceleration of no. 3?

11. We can deduce that:We can deduce that:
Acceleration, Acceleration, aa is directly is directly
proportional to the proportional to the resultant resultant
force, force, FF and inversely and inversely
proportional to the proportional to the mass, mass, mm..
a = —
F
m

12. NEWTON’S THIRD LAWNEWTON’S THIRD LAW
FOR EVERY
ACTION THERE
MUST BE AN
EQUAL AND
OPPOSITE
REACTION FORCE

13. Newton’s Third Law ExplainedNewton’s Third Law Explained
There can be no force unless two
bodies are involved . When a
hammer strikes a nail, it exerts an
“action” force on the nail. But the
nail must also “react” by pushing
back against the hammer. In all
cases, there must be an acting force
and a reacting force. Whenever two
bodies interact, the force exerted by
the second body on the first (the
reaction force) is equal in magnitude
and opposite in direction to the force
exerted by the first body n the
second (the action force).

14. Illustrating the 3Illustrating the 3
rdrd
Law of Motion Law of Motion
The wheels of
the car push
on the road.
The road pushes
the wheels of the
car.
ACTION FORCE:
REACTION FORCE:

15. THANK YOU FOR LISTENING!THANK YOU FOR LISTENING!
That’s all folks. That’s all folks.
Got it?Got it?