NEWTONS LAWS OF MOTION.pptx
- 1. AARYAMAN PRATAP SINGH CLASS XI THE MILLANIUM SCHOOL, SECTOR 58 MOHALI
- 2. BACKGROUND Sir Isaac Newton (1643-1727) an English scientist and mathematician famous for his discovery of the law of gravity also discovered the three laws of motion. He published them in his book Philosophiae Naturalis Principia Mathematica (mathematic principles of natural philosophy) in 1687. Today these laws are known as Newtons Laws of Motion and describe the motion of all objects on the scale we experience in our everyday lives.
- 4. While most people know what Newton's laws say, many people do not know what they mean (or simply do not believe what they mean).
- 5. Newtons Laws of Motion 1st Law An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force. 2nd Law The second law states that the force on an object is equal to its mass times its acceleration. 3rd Law For every action there is an equal and opposite reaction.
- 6. 1st Law of Motion (Law of Inertia) An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.
- 7. Newtons First Law is also called the Law of Inertia Inertia: the tendency of an object to resist changes in its state of motion The First Law states that all objects have inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).
- 8. 1st Law Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. These pumpkins will not move unless acted on by an unbalanced force.
- 9. 1st Law Once airborne, unless acted on by an unbalanced force (gravity and air fluid friction), it would never stop!
- 10. 1st Law Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.
- 11. Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force? Its a force we sometimes cannot see friction.
- 12. There are four main types of friction: Sliding friction: ice skating Rolling friction: bowling Fluid friction (air or liquid): air or water resistance Static friction: initial friction when moving an object What is this unbalanced force that acts on an object in motion?
- 13. 際際滷 a book across a table and watch it slide to a rest position. The book comes to a rest because of the presence of a force - that force being the force of friction - which brings the book to a rest position. In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.)
- 14. Some Examples from Real Life Two teams are playing tug of war. They are both exerting equal force on the rope in opposite directions. This balanced force results in no change of motion. A soccer ball is sitting at rest. It takes an unbalanced force of a kick to change its motion.
- 15. In outer space, away from gravity and any sources of friction, a rocket ship launched with a certain speed and direction would keep going in that same direction and at that same speed forever.
- 16. Newtonss 1st Law andYou Dont let this be you. Wear seat belts. Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.
- 17. Newtons Second Law Force equals mass times acceleration. F = ma Acceleration: a measurement of how quickly an object is changing speed.
- 18. 2nd Law
- 19. 2nd Law The net force of an object is equal to the product of its mass and acceleration, or F=ma.
- 20. What does F = ma mean? Force is directly proportional to mass and acceleration. Imagine a ball of a certain mass moving at a certain acceleration. This ball has a certain force. Now imagine we make the ball twice as big (double the mass) but keep the acceleration constant. F = ma says that this new ball has twice the force of the old ball. Now imagine the original ball moving at twice the original acceleration. F = ma says that the ball will again have twice the force of the ball at the original acceleration.
- 21. More about F = ma If you double the mass, you double the force. If you double the acceleration, you double the force. What if you double the mass and the acceleration? (2m)(2a) = 4F Doubling the mass and the acceleration quadruples the force. So . . . what if you decrease the mass by half? How much force would the object have now?
- 22. Newtons 2nd Law proves that different masses accelerate to the earth at the same rate, but with different forces. We know that objects with different masses accelerate to the ground at the same rate. However, because of the 2nd Law we know that they dont hit the ground with the same force. F = ma 98 N = 10 kg x 9.8 m/s/s F = ma 9.8 N = 1 kg x 9.8 m/s/s
- 23. 3rd LAW OF MOTION For every action, there is an equal and opposite reaction.
- 24. Newtons 3rd Law in Nature Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards).
- 25. 3rd Law Flying gracefully through the air, birds depend on Newtons third law of motion. As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.
- 26. Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. In turn, the air reacts by pushing the bird upwards. The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). Action-reaction force pairs make it possible for birds to fly.
- 28. 3rd Law Consider the motion of a car on the way to school. A car is equipped with wheels which spin backwards. As the wheels spin backwards, they grip the road and push the road backwards.
- 29. 3rd Law The reaction of a rocket is an application of the third law of motion. Various fuels are burned in the engine, producing hot gases. The hot gases push against the inside tube of the rocket and escape out the bottom of the tube. As the gases move downward, the rocket moves in the opposite direction.
- 30. Think about it . . . What happens if you are standing on a skateboard or a slippery floor and push against a wall? You slide in the opposite direction (away from the wall), because you pushed on the wall but the wall pushed back on you with equal and opposite force. Why does it hurt so much when you stub your toe? When your toe exerts a force on a rock, the rock exerts an equal force back on your toe. The harder you hit your toe against it, the more force the rock exerts back on your toe (and the more your toe hurts).
- 31. Review Newtons First Law: Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force. Newtons Second Law: Force equals mass times acceleration (F = ma). Newtons Third Law: For every action there is an equal and opposite reaction.
- 32. Vocabulary Inertia: the tendency of an object to resist changes in its state of motion Acceleration: a change in velocity a measurement of how quickly an object is changing speed, direction or both Velocity: The rate of change of a position along a straight line with respect to time Force: strength or energy