1) Newton's third law of motion states that for every action, there is an equal and opposite reaction. 2) Whenever one object exerts a force on a second object, the second object exerts an equal but opposite force back on the first object. These paired forces are called action-reaction force pairs. 3) Examples of action-reaction force pairs include a rocket exhaust pushing down on gases which push back up on the rocket with an equal force, and a car tire pushing down on the road surface while the road pushes back up on the tire.

1. ACTION-REACTION
Joy U. Fulgar
THIRD LAW OF MOTION:
NEWTON’S

2. INTERACTIONS PRODUCE FORCES
•FORCE is a push or pull.
•The forces exerted by two objects on each other
are often called an action-reaction force pair.

3. “For every action,
is an equal and
reaction”

4. Whenever one object
exerts a force on a second
object, the second object
exerts an equal but
opposite force on the
first object.

5. •One force is called the
force and the
other force is called the
force.
•Neither force can exist
without the other.

6. IDENTIFYING ACTION & REACTION
•Object A exerts a force on Object
B
then in reverse
Object B exerts a force on object
A

7. •The reaction force is the
upward push on the rocket
engine by the gas molecules.
•This downward push is
the action force.
IDENTIFYING ACTION & REACTION

9. Action: tire pushes on road
Reaction: road pushes on tire

10. IDENTIFYING ACTION & REACTION

11. IDENTIFYING ACTION & REACTION
•Action: Tyre pushes road
•Reaction: Road pushes tyre

12. IDENTIFYING ACTION & REACTION

13. IDENTIFYING ACTION & REACTION
•Action: Rocket pushes gas
•Reaction: Gas pushes rocket

15. ACTION AND REACTION ON
DIFFERENT MASSES
•A bug with a mass of 5
grams flies into the
windshield of a moving
1000kg bus.
•Which will have the most
force?
•The bug on the bus
•The bus on the bug

16. ACTION AND REACTION ON
DIFFERENT MASSES
Consider a cannon and cannon ball.
According to Newton’s second law we must
consider the masses.
Cannon ball: F/m = a
Cannon: F/m = a

17. THINK!
•The astronauts working on the space
station have a serious problem when
they need to move around in space:
There is nothing to push on.
One solution is to throw
something opposite the
direction you want to

18. WHY DON'T ACTION & REACTION
FORCES CANCEL?
•"If pushes , then pushes with an equal
and opposite force. If these forces are equal
and opposite, they cancel, producing a net
force of zero. This means that neither object
can accelerate, which means that Newton's
Laws predict that nothing can ever move."

19. •These forces DO NOT CANCEL because they
influence the motion of different objects. The
force that exerts on influences 's motion,
and the force that exerts on influences 's
motion. The force on B can cancel with other
forces on - but NOT with forces on (and
vice versa).

20. REFERENCES:
• Amrita.olabs.co.in,. (2012). Newton's Third law of Motion. Retrieved from December
2015, from amrita.olabs.co.in/?sub=1&brch=1&sim=105&cnt=1
• http://physics.stackexchange.com/questions/103814/action-and-reaction-pair-
problem
• Newton's Third Law of Motion (2010). Retrieved from
• http://www.4physics.com/phy_demo/newton/newton_3.htm
• https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/third_law_motion.html