Newton's laws


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Newton's laws

  1. 1. TEKS: 8.3C 8.3 Scientific Investigation and Reasoning. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions and knows the contributions of relevant scientists. The student is expected to: (D) relate the impact of research on scientific thought and society, including the history of science and contributions of scientists as related to the content.
  2. 2. TEKS: 8.6C 8.6 Force, motion, and energy. The student knows that there is a relationship between force, motion, and energy. The student is expected to: (C) investigate and describe applications of Newton’s law of inertia, law of force and acceleration, and law of action-reaction such as in vehicle restraints, sports activities, amusement park rides, Earth’s tectonic activities*, and rocket launches. *Will be covered in 3rd Six Weeks.
  3. 3. • One of the most influential scientists of all time • English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian • Invented a reflecting telescope, which brought him much fame and attention (1668) • Wrote Principia Mathematica, one of the most influential science books in history (discusses universal gravitation and laws of motion) (1687)
  4. 4. An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Also called the law of inertia.
  5. 5. • In other words an object will keep doing whatever it’s doing (still or moving) unless an unbalanced force acts on it. • Example: Your skateboard will stay lying in the driveway until someone moves it. And, if your skateboard suddenly hits a curb and stops short… you will keep moving until something stops you!
  6. 6. • Newton’s 1st law is also known as the Law of Inertia.Inertia. (Inertia is an object’s(Inertia is an object’s tendency to resist a change intendency to resist a change in motion.)motion.) • The greater an object’s mass, the greaterThe greater an object’s mass, the greater its inertia, and the larger the force neededits inertia, and the larger the force needed to overcome the overcome the inertia. •Which vehicle would take longer to stop? •It will take longer for the dump truck to stop than the car, because the dump truck has more mass.
  7. 7. A property of matter The tendency of an object to resist any change in its motion The greater the mass the greater the inertia The greater the speed the greater the inertia All About Inertia
  8. 8. Examples of Newton’s 1st Law • car suddenly stops and you strain against the seat belt because our bodies want to keep moving • when riding a horse, the horse suddenly stops and you fly over its head • the difficulty of pushing a dead car • car turns left and you appear to slide to the right • ketchup stays in the bottom (at rest) until you bang (outside force) on the end of the bottom • a headrest in a car prevents whiplash injuries during a rear-end collision (your head goes forward and then jerks backward)
  9. 9. Newtons’s 1st 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 (includingBecause of inertia, objects (including you) resist changes in their motion. Whenyou) resist changes in their motion. When the car going 80 km/hour is stopped bythe car going 80 km/hour is stopped by the brick wall, your body keeps moving atthe brick wall, your body keeps moving at 80 m/hour.80 m/hour.
  10. 10. Newton’s 2nd Law Force= mass x acceleration
  11. 11. Second law: The greater the force applied to an object, the more the object will accelerate. It takes more force to accelerate an object with a lot of mass than to accelerate something with very little mass. The player in black had more acceleration thus he hit with a greater amount of force
  12. 12. Second law: The greater the force, the greater the acceleration The greater the mass, the greater the force needed for the same acceleration Calculated by: F = ma (F = force, m = mass, a = acceleration)
  13. 13. 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 = maF = ma 98 N = 10 kg x 9.8 m/s/s98 N = 10 kg x 9.8 m/s/s F = maF = ma 9.8 N = 1 kg x 9.89.8 N = 1 kg x 9.8 m/s/sm/s/s
  14. 14. Examples of Newton’s 2nd Law • hitting a baseball, the harder the hit, the faster the ball goes • accelerating or decelerating a car •The positioning of football players – massive players on the line with lighter (faster to accelerate) players in the backfield • a loaded truck versus an unloaded truck
  15. 15. Newton’s 3rd Law • For every action force, there is an equal and opposite reaction force. (Forces are always found in pairs.) • Athlete pushes bar upwards. • Bar pushes the athlete downwards. • Bowling ball pushes pin to the right. • Pin pushes bowling ball to the left.
  16. 16. Newton’s 3rd Law
  17. 17. 3rd Law Reaction of a rocket. FuelsReaction of a rocket. Fuels are burned in the engine,are burned in the engine, producing hot gases.producing hot gases. The hot gases push againstThe hot gases push against the inside tube of the rocketthe inside tube of the rocket and escape out the bottom ofand escape out the bottom of the tube. As the gases movethe tube. As the gases move downward, the rocketdownward, the rocket moves in the oppositemoves in the opposite direction.direction.
  18. 18. Examples 3rd Law •Momentum of the car moving forward and the car comes to a sudden stop, our body pushes against the seat (action) belt and the seat belt pushes back (reaction). •When you lean on the wall to rest, the weight on the wall provides the reaction force and the wall pushes back on you (reaction force) with the same force. • Roller coaster ride- The train to the tracks. •Birds wings to the air.
  19. 19. Car to the tracks- 3rd Law