Physics 3rd w11
- 1. PHYSICS ACTION AND REACTION: NEWTON’S THIRD LAW. Teacher: Telman Askeraliyev, MSc, Italy
- 2. NEWTON’S THIRD LAW For every action force, there must be an equal and opposite reaction force. Forces occur in pairs. Action Reaction Action Reaction
- 3. ACTING AND REACTING FORCES The action force is exerted by the _____ on the _____. The reaction force is exerted by the _____ on the _____. bar hands bar hands Action Reaction
- 4. ACTING AND REACTING FORCES In every interaction, the forces always occur only in pairs, BUT these forces act on two different bodies. Common definition: - to every action there is an equal and opposite reaction is very dangerous, so please do not use it. It is not defined what is action and what is reaction, so it looks as if we were talking about one body, but that’s not true. These forces act on different bodies.
- 5. ACTION - REACTION •When the rocket fuel is ignited, a hot gas is produced. •As the gas molecules collide with the inside engine walls, the walls exert a force that pushes them out of the bottom of the engine.
- 6. ACTION - REACTION •This downward push is the action force. •The reaction force is the upward push on the rocket engine by the gas molecules. •This is the thrust that propels the rocket upward.
- 7. EXPERIMENT - WATER ROCKET EXPERIMENT
- 8. NORMAL FORCE
- 9. NORMAL FORCE
- 10. EXAMPLES You push the water backward, the water pushes you forward.
- 11. EXAMPLES action: tire pushes road reaction: road pushes tire
- 12. EXAMPLES action: foot pushes the ground reaction: the ground pushes the foot that propels the turtle forward
- 13. EXAMPLES action: cannon pushes the cannonball reaction: cannonball pushes the cannon (recoil) The same force F (opposite direction)
- 14. THIRD LAW To every action, there is always an opposed but equal reaction. More formally, the law states that for every force exerted by object A on object B, there is an equal but opposite force exerted by object B on object A. FAB = –FBA
- 15. THIRD LAW For example, when you hit your hand against your desk, your hand exerts a force on the desk. Simultaneously, the desk exerts a force of equal magnitude in the opposite direction on your hand. Physical contact is not necessary for Newton’s third law; the mutual gravitational pull between the Earth and the Moon traverses hundreds of thousands of kilometers of space.
- 16. 1 - QUIZ A 60-kg athlete exerts a force on a 10-kg skateboard. If she receives an acceleration of 4 m/s2, what is the acceleration of the skateboard?
- 17. 2 - QUIZ A woman riding a bicycle collides head-on with a parked school bus. Which object feels greater force?
- 18. 3 - QUIZ Explain Newton’s third law of motion.
- 19. 4 - QUIZ If they are “equal but opposite,” why don’t action-reaction pairs cancel?
- 20. 5 - QUIZ If you hold a backpack in you hand, the force of gravity pulls it downward. What force keeps it from falling to the ground?
- 22. THANK YOU!