Physics day2
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Physics day2

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PSHS 3rd Year Physics

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 Physics day2 Presentation Transcript

  • PSHS PHYSICS 3RD YEAR
    Session 2
  • The right tools to succeed in 2nd quarter physics
    Know TRIGONOMETRY
    Yes, math and physics are very much related! 
    Know VECTORS
    Know NEWTON’S LAWS
    Know how to make An FBD (Free Body Diagram)
  • How to master the tools?
    READ your physics book.
    ANSWER EXERCISES in the book, and verify the answers at the back of the book.
    View slide
  • TRIGONOMETRY
    Use SOHCAHTOA
    Set a REFERENCE xy-plane
    Opposite of what?
    The REFERENCE ANGLE .
    View slide
  • Practice!
  • VECTORS
    Operations on vectors
    Finding the resultant, given two or more vectors
    Finding a missing vector, given the other vectors and the resultant vector
  • Method 1: Tail-to-tip(graphical)
    Tip of B
    Tail of A
  • Method 2: Parallelogram(graphical also)
  • Tail-to-tip AND Parallelogram:Which is which?
    Parallelogram
    Tail-to-tip
  • Subtraction of vectors
    Given a vector A, the negative of A (or –A) is a vector of the same magnitude, but in the opposite direction
  • Subtraction of vectors
  • Method 3: Component method(computational)
    B = 26.5
    A = 44.0
    C = 31.0
  • Resolve each vector into its x- and y-components
    B = 26.5
    A = 44.0
    C = 31.0
  • Projectile Motion: The object’s motion has both x- and y-components.
    What is the difference between the object’s horizontal (x) component and its vertical (y) component?
    x-component:
    Uniform velocity
    Given: an object
    thrown with a
    horizontal velocity
    y-component:
    Accelerating downward
  • 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.
  • Formulas you should know:
  • 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.
    When getting the total time, should we use the equations for the vertical or the horizontal?
    EITHER will do.
    c.) the total horizontal distance covered.
  • NEWTON’S LAWS OF MOTION
  • Newton’s First Law
    Law of Inertia
    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.
    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?
    NOT A FORCE. The backpacks continue their state of motion.
  • Newton’s Second Law
    F = ma
    The acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass.
    The direction of the acceleration is in the direction of the net force acting on the object.
    What happens when a net force is exerted on a body/object?
  • Newton’s Third Law
    Action and Reaction
    Whenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first.
    Why does a rocket accelerate upward?
  • Is mass the same as weight?
    Mass – the amount of matter in an object
    - unit: kilograms
    • Weight – gravitational force on an object due to the downward acceleration of gravity. It is always directed downward (direct south).
    - unit: Newtons
    Object at rest: no NET force acting on it
  • 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.
    a.) Determine the weight of the box and the normal force exerted on it by the table.
  • 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.
    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?
  • 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.
    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?