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# Newtons laws

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### Newtons laws

1. 1. Newton’s Laws of Motion
2. 2. Force  Two types of forces  Contact force  Force caused by physical contact  Field force  Force caused by gravitational attraction between two objects
3. 3. Isaac Newton  Born 1642  Went to University of Cambridge in England as a student and taught there as a professor after  Never married  Gave his attention mostly to physics and mathematics, but he also gave his attention to religion and alchemy  Newton was the first to solve three mysteries that intrigued the scientists  Laws of Motion  Laws of Planetary Orbits  Calculus
4. 4. Three Laws of Motion  Newton’s Laws of Motion are laws discovered by Physicist and mathematician, Isaac Newton, that explains the objects’ motions depending on forces acted on them  Newton’s First Law: Law of Inertia  Newton’s Second Law: Law of Resultant Force  Newton’s Third Law: Law of Reciprocal Action
5. 5. Newton’s First Law  An Object at rest remains at rest, and an object in motion continues in motion with constant velocity (that is, constant speed in a straight line), unless it experiences a net external force.  The tendency to resist change in motion is called inertia  People believed that all moving objects would eventually stop before Newton came up with his laws
6. 6. Friction  A force that causes resistance to motion  Arises from contact between two surfaces  If the force applied is smaller than the friction, then the object will not move  If the object is not moving, then ffriction=Fapplied  The object eventually slips when the applied force is big enough
7. 7. Friction  Friction was discovered by Galileo Galilee when he rolled a ball down a slope and observed that the ball rolls up the opposite slope to about the same height, and concluded that the difference between the initial height and the final height is caused by friction.  Galileo also noticed that the ball would roll almost forever on a flat surface so that the ball can elevate to the same height as where it started.
8. 8. Two types of Friction  Static Friction  Friction that exists while the object is stationary  If the applied force on an object becomes greater than the maximum of static friction, then the object starts moving  fstatic≤μstaticn  Kinetic Friction  The friction that exists when an object is in motion  F-fkinetic produces acceleration to the direction the object is moving  If F=fkinetic, then the object moves at constant speed with no acceleration  fkinetic= μkineticn  Kinetic friction and the coefficient of kinetic friction are smaller than static friction and the static coefficient
9. 9. Newton’s First Law  When there is no force exerted on an object, the motion of the object remains the same like described in the diagram  Because the equation of Force is F=ma, the acceleration is 0m/s². So the equation is 0N=m*0m/s²  Therefore, force is not needed to keep the object in motion, when  The object is in equilibrium when it does not change its state of motion
10. 10. The car is traveling rightward and crashes into a brick wall. The brick wall acts as an unbalanced force and stops the car.
11. 11. The truck stops when it crashes into the red car. But the ladder falls in front of the truck because the ladder was in motion with the truck but there is nothing stopping the ladder when the truck stops.
12. 12. Newton’s Second Law  The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass Fnet Acceleration
13. 13. Unbalanced Force and Acceleration  Force is equal to acceleration multiplied by mass  When an unbalanced force acts on an object, there is always an acceleration  Acceleration differs depending on the net force  The acceleration is inversely related to the mass of the object
14. 14. Net Force  Force is a vector  Because it is a vector, the net force can be determined by subtracting the force that resists motion from the force applied to the object.  If the force is applied at an angle, then trigonometry is used to find the force Fnet
15. 15. θ R R*cos θ R*sin θ θ R
16. 16. Gravitational Force  The force that exerts all objects toward the earth’s surface is called a gravitational force.  The magnitude of the gravitational force is called weight  The acceleration due to gravity is different in each location, but 9.80m/s² is most commonly used  Calculated with formula w=mg
17. 17. Newton’s Third Law  If two objects interact, the force exerted on object 1 by object 2 is equal in magnitude but opposite in direction to the force exerted on object 2 by object 1  Forces always come in pair when two objects interact  The forces are equal, but opposite in direction Fg Fn
18. 18. As the man jumps off the boat, he exerts the force on the boat and the boat exerts the reaction force on the man. The man leaps forward onto the pier, while the boat moves away from the pier. Newton’s Third Law
19. 19. Force exerted by the wheels Force exerted by the road Newton’s Third Law
20. 20. Newton’s Third Law Flow backward Foil deflected down Foil deflected up Engine pushed forward Flow pushed backward Foil deflected down