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Transcript of Rajat manchanda
1. POWERPOINTPRESENTATION 2. Newtons Laws of Motion I. Law of Inertia II. F=ma III. Action-Reaction 3. Newtons Laws of Motion 1st Law An object at rest will stay atrest, and an object in motion will stay inmotion at constant velocity, unless actedupon by an unbalanced force. 2nd Law Force equals mass timesacceleration. 3rd Law For every action there is anequal and opposite reaction. 4. 1st Law of Motion(Law of Inertia)An object at rest will stay atrest, and an object in motionwill stay in motion atconstant velocity, unless actedupon by an unbalanced force. 5. 1st Law Onceairborne, unlessacted on by anunbalanced force(gravity and air fluidfriction), itwould neverstop! 6. DO U KNOW? Why then, do we observe everyday objects in motion slowingdown and becoming motionlessseemingly without an outsideforce? Its a force we sometimes cannot see friction. 7. What is this unbalanced force that acts on an object in motion? 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 anobject 8. TRY ITSlide a bookacross a table andwatch it slide to a restposition. The bookcomes to a restbecause of thepresence of a force -that force being theforce of friction -which brings the bookto a rest position. 9. Newtonss 1st Law and YouDont let this be you. Wear seat belts.Because of inertia, objects (including you) resist changesin their motion. When the car going 80 km/hour is stoppedby the brick wall, your body keeps moving at 80 m/hour. 10. 2nd LawThe net force of an object isequal to the product of its massand acceleration, or F=ma. 11. 2nd Law 12. 2nd Law When mass is in kilograms and acceleration isin m/s/s, the unit of force is in newtons (N). One newton is equal to the force required toaccelerate one kilogram of mass at onemeter/second/second. 13. 2nd Law (F = m x a) How much force is needed to accelerate a 1400kilogram car 2 meters per second/per second? Write the formula F=mxa Fill in given numbers and units F = 1400 kg x 2 meters per second/second Solve for the unknown 2800 kg-meters/second/second or 2800 N 14. If mass remains constant, doubling the acceleration, doubles the force. If force remainsconstant, doubling the mass, halves the acceleration. 15. Newtons 2nd Law proves that different massesaccelerate to the earth at the same rate, but withdifferent forces. We know that objectswith different massesaccelerate to theground at the samerate. However, because ofthe 2nd Law we knowthat they dont hit theground with the sameforce. F = ma F = ma 98 N = 10 kg x 9.8 m/s/s 9.8 N = 1 kg x 9.8 m/s/s 16. Check Your Understanding 1. What acceleration will result when a 12 N net force applied to a 3 kgobject? A 6 kg object? 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2.Determine the mass. 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 9.8m/sec/sec? 17. Check Your Understanding 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 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine themass.16 N = 3.2 kg x 5 m/s/s 3. How much force is needed to accelerate a 66 kg skier 1 m/s2? 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/s2? 9800 kg-m/sec/sec or 9800 N 18. 3rd Law For every action, there is anequal and opposite reaction. 19. 3rd Law According to Newton, whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body. 20. 3rd LawThere are two forcesresulting from thisinteraction - a force onthe chair and a force onyour body. These twoforces are called actionand reaction forces. 21. Newtons 3rd Law in Nature Consider the propulsion of afish through the water. Afish uses its fins to pushwater backwards. In turn,the water reacts by pushingthe fish forwards, propellingthe fish through the water.The size of the force on thewater equals the size of theforce on the fish; thedirection of the force on thewater (backwards) isopposite the direction of theforce on the fish (forwards). 22. 3rd LawFlying gracefullythrough the air, birdsdepend on Newtonsthird law of motion. Asthe birds push down onthe air with their wings,the air pushes theirwings up and givesthem lift. 23. 3rd Law Consider the motion ofa car on the way toschool. A car isequipped with wheelswhich spin backwards.As the wheels spinbackwards, they grip theroad and push the roadbackwards. 24. 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.