Physics day2

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PSHS 3rd Year Physics
Batch 2013
Newton's Laws of Motion
Vector Addition
Free body diagram of box on a table

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Physics day2

  1. 1. PSHS PHYSICS 3RD YEAR<br />Session 2<br />
  2. 2. The right tools to succeed in 2nd quarter physics<br />Know TRIGONOMETRY<br />Yes, math and physics are very much related! <br />Know VECTORS<br />Know NEWTON’S LAWS<br />Know how to make An FBD (Free Body Diagram)<br />
  3. 3. How to master the tools?<br />READ your physics book. <br />ANSWER EXERCISES in the book, and verify the answers at the back of the book.<br />
  4. 4. TRIGONOMETRY<br />Use SOHCAHTOA<br />Set a REFERENCE xy-plane<br />Opposite of what?<br />The REFERENCE ANGLE .<br />
  5. 5. Practice!<br />
  6. 6. VECTORS<br />Operations on vectors<br />Finding the resultant, given two or more vectors<br />Finding a missing vector, given the other vectors and the resultant vector<br />
  7. 7. Method 1: Tail-to-tip(graphical)<br />Tip of B<br />Tail of A<br />
  8. 8. Method 2: Parallelogram(graphical also)<br />
  9. 9. Tail-to-tip AND Parallelogram:Which is which?<br />Parallelogram<br />Tail-to-tip<br />
  10. 10. Subtraction of vectors<br />Given a vector A, the negative of A (or –A) is a vector of the same magnitude, but in the opposite direction<br />
  11. 11. Subtraction of vectors<br />
  12. 12. Method 3: Component method(computational)<br />B = 26.5<br />A = 44.0<br />C = 31.0<br />
  13. 13. Resolve each vector into its x- and y-components<br />B = 26.5<br />A = 44.0<br />C = 31.0<br />
  14. 14. Projectile Motion: The object’s motion has both x- and y-components.<br />What is the difference between the object’s horizontal (x) component and its vertical (y) component?<br />x-component:<br />Uniform velocity<br />Given: an object<br /> thrown with a <br />horizontal velocity<br />y-component:<br />Accelerating downward<br />
  15. 15. FROM YOUR DIAGNOSTIC:A projectile is fired with an initial speed of 65.2 m/s at an angle of above the horizontal on a long flat firing range. Determine: a) maximum height.<br />
  16. 16. Formulas you should know:<br />
  17. 17. FROM YOUR DIAGNOSTIC:A projectile is fired with an initial speed of 65.2 m/s at an angle of above the horizontal on a long flat firing range. Determine: b) total time in the air.<br />When getting the total time, should we use the equations for the vertical or the horizontal?<br />EITHER will do.<br />c.) the total horizontal distance covered.<br />
  18. 18. NEWTON’S LAWS OF MOTION<br />
  19. 19. Newton’s First Law<br />Law of Inertia<br /> Every object continues in its state of rest, or of uniform velocity in a straight line, as long as no net force acts on it. <br /> A school bus comes to a sudden stop, and all the backpacks on the floor start to slide forward. What force causes them to do that?<br /> NOT A FORCE. The backpacks continue their state of motion.<br />
  20. 20. Newton’s Second Law<br />F = ma<br />The acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass.<br />The direction of the acceleration is in the direction of the net force acting on the object.<br />What happens when a net force is exerted on a body/object?<br />
  21. 21. Newton’s Third Law<br />Action and Reaction<br />Whenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first.<br />Why does a rocket accelerate upward?<br />
  22. 22.
  23. 23. Is mass the same as weight?<br />Mass – the amount of matter in an object<br />- unit: kilograms<br /><ul><li>Weight – gravitational force on an object due to the downward acceleration of gravity. It is always directed downward (direct south).</li></ul>- unit: Newtons<br />Object at rest: no NET force acting on it<br />
  24. 24. Exercise: A friend has given you a special gift, a box of mass 10.0 kg. The box is resting on the smooth (frictionless) horizontal surface of a table. <br />a.) Determine the weight of the box and the normal force exerted on it by the table.<br />
  25. 25. Exercise: A friend has given you a special gift, a box of mass 10.0 kg. The box is resting on the smooth (frictionless) horizontal surface of a table. <br />b.) Now your friend pushes down on the box with a force of 40.0 N. What is the normal force exerted on the box by the table?<br />
  26. 26. Exercise: A friend has given you a special gift, a box of mass 10.0 kg. The box is resting on the smooth (frictionless) horizontal surface of a table. <br />c.) If your friend pulls upward on the box with a force of 40.0 N, what now is the normal force exerted on the box by the table?<br />

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