the different laws of motion by Isaac Newton.ppt
- 1. Newton’s Newton’s Laws of Laws of Motion Motion I. I. Law of Inertia Law of Inertia II. II. F=ma F=ma III. III. Action-Reaction Action-Reaction
- 2. While most people know While most people know what Newton's laws say, what Newton's laws say, many people do not know many people do not know what they mean (or simply do what they mean (or simply do not believe what they mean). not believe what they mean).
- 3. Newton’s Laws of Motion Newton’s Laws of Motion 1 1st st Law Law – An object at rest will stay at rest, – An object at rest will stay at rest, and an object in motion will stay in and an object in motion will stay in motion at constant velocity, unless acted motion at constant velocity, unless acted upon by an unbalanced force. upon by an unbalanced force. 2 2nd nd Law Law – – Force equals mass times Force equals mass times acceleration. acceleration. 3 3rd rd Law Law – – For every action there is an For every action there is an equal and opposite reaction. equal and opposite reaction.
- 4. 1 1st st Law of Motion Law of Motion (Law of Inertia) (Law of Inertia) An object at rest will stay at An object at rest will stay at rest, and an object in motion rest, and an object in motion will stay in motion at will stay in motion at constant velocity, unless acted constant velocity, unless acted upon by an unbalanced force. upon by an unbalanced force.
- 5. 1 1st st Law Law Inertia is the Inertia is the tendency of an tendency of an object to resist object to resist changes in its changes in its velocity: velocity: whether in whether in motion or motion or motionless. motionless. These pumpkins will not move unless acted on by an unbalanced force.
- 6. 1 1st st Law Law Once airborne, Once airborne, unless acted on unless acted on by an by an unbalanced force unbalanced force (gravity and air (gravity and air – fluid friction), – fluid friction), it would never it would never stop! stop!
- 7. 1 1st st Law Law Unless acted Unless acted upon by an upon by an unbalanced unbalanced force, this golf force, this golf ball would sit on ball would sit on the tee forever. the tee forever.
- 8. Why then, do we observe Why then, do we observe every day objects in motion every day objects in motion slowing down and becoming slowing down and becoming motionless seemingly without an motionless seemingly without an outside force? outside force? It’s a force we sometimes cannot see – It’s a force we sometimes cannot see – friction. friction.
- 9. Objects on earth, unlike the Objects on earth, unlike the frictionless space the moon frictionless space the moon travels through, are under the travels through, are under the influence of friction. influence of friction.
- 10. There are four main types of friction: There are four main types of friction: Sliding friction: Sliding friction: ice skating Rolling friction: Rolling friction: bowling Fluid friction (air or liquid): Fluid friction (air or liquid): air or water resistance Static friction: Static friction: initial friction when moving an object What is this unbalanced force that acts on an object in motion? What is this unbalanced force that acts on an object in motion?
- 11. Slide a book Slide a book across a table and across a table and watch it slide to a rest watch it slide to a rest position. The book position. The book comes to a rest comes to a rest because of the because of the presence presence of a force - of a force - that force being the that force being the force of friction - force of friction - which brings the book which brings the book to a rest position. to a rest position.
- 12. In the absence of a force of friction, the book In the absence of a force of friction, the book would continue in motion with the same speed would continue in motion with the same speed and direction - forever! (Or at least to the end and direction - forever! (Or at least to the end of the table top.) of the table top.)
- 13. Newtons’s 1 Newtons’s 1st st Law and You Law and You Don’t let this be you. Wear seat belts. Don’t let this be you. Wear seat belts. Because of inertia, objects (including you) resist changes Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 m/hour. by the brick wall, your body keeps moving at 80 m/hour.
- 14. 2 2nd nd Law Law
- 15. 2 2nd nd Law Law The net force of an object is The net force of an object is equal to the product of its mass equal to the product of its mass and acceleration, or F=ma. and acceleration, or F=ma.
- 16. 2 2nd nd Law Law When mass is in kilograms and acceleration is When mass is in kilograms and acceleration is in m/s/s, the unit of force is in newtons (N). in m/s/s, the unit of force is in newtons (N). One newton is equal to the force required to One newton is equal to the force required to accelerate one kilogram of mass at one accelerate one kilogram of mass at one meter/second/second. meter/second/second.
- 17. 2 2nd nd Law (F = m x a) Law (F = m x a) How much force is needed to accelerate a 1400 kilogram car 2 meters per second/per second? Write the formula Write the formula F = m x a Fill in given numbers and units Fill in given numbers and units F = 1400 kg x 2 meters per second/second Solve for the unknown Solve for the unknown 2800 kg-meters/second/second or 2800 N
- 18. If mass remains constant, doubling the acceleration, doubles the force. If force remains constant, doubling the mass, halves the acceleration.
- 19. Newton’s 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 don’t hit the ground with the same force. F = ma F = ma 98 N = 10 kg x 9.8 m/s/s 98 N = 10 kg x 9.8 m/s/s F = ma F = ma 9.8 N = 1 kg x 9.8 9.8 N = 1 kg x 9.8 m/s/s m/s/s
- 21. Check Your Understanding Check Your Understanding 1. What acceleration will result when a 12 N net force applied to a 3 kg 1. What acceleration will result when a 12 N net force applied to a 3 kg object? A 6 kg object? object? A 6 kg object? 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2 2 . . Determine the mass. Determine the mass. 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec? 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec? 4. What is the force on a 1000 kg elevator that is falling freely at 9.8 4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec? m/sec/sec?
- 22. Check Your Understanding Check Your Understanding 1. What acceleration will result when a 12 N net force applied to a 3 kg object? 1. What acceleration will result when a 12 N net force applied to a 3 kg object? 12 N = 3 kg x 4 m/s/s 12 N = 3 kg x 4 m/s/s 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2 2 . Determine the . Determine the mass. mass. 16 N = 3.2 kg x 5 m/s/s 16 N = 3.2 kg x 5 m/s/s 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec? 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec? 66 kg-m/sec/sec or 66 N 66 kg-m/sec/sec or 66 N 4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec? 4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec/sec? 9800 kg-m/sec/sec or 9800 N 9800 kg-m/sec/sec or 9800 N