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Free fall motion-part 1


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Free fall motion-part 1

  1. 1. Falling Objects<br />
  2. 2. What is physics exactly? <br />The branch of science concerned with the nature and properties of matter and energy.<br />The study of the physical world<br />Includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms<br />
  3. 3. All objects “fall” at same rate near the surface of the earth, & in the absence of friction<br />Objects will fall at constant acceleration (at the rate of acceleration due to gravity)<br />By “fall”, we are referring to the rate at which velocity changes<br />And I’m free… falling!<br />
  4. 4. SI units: <br />ay = g = -9.81 m/s2<br />The velocity of an object changes 9.81 m/s every second. <br />English units: <br />ay = g = -32.2 ft/s2<br />The velocity of an object changes 32.2 m/s every second. <br />Acceleration due to gravity<br />
  5. 5. Acceleration due to gravity<br />
  6. 6. It NEVER ceases to exist<br />It ALWAYS works DOWN<br />It is NEVER zero<br />Acceleration due to gravity<br />
  7. 7. For vertical motion, we use the same kinematic equations as before: <br />In your book: xi, xf, Δx become yi, yf, Δy<br />In your book: Acceleration (a) is g<br />Analyzing falling objects using kinematic equations<br />
  8. 8. Negative & positive signs are VERY important in vertical motion<br />MUST be consistent<br />G is negative<br />Vertical downward displacement away from origin is negative<br />Vertical upward displacement away from origin is positive<br />Acceleration due to gravity<br />
  9. 9. A ball is dropped from a tower 70.0 m high. If we neglect air friction, determine how far the ball has fallen after:<br />1.00 s<br />2.00 s<br />3.00 s<br />Problem Solving Strategy:<br />Identify knowns:<br />Xi  yi<br />Xi  Yf<br />Vi<br />Vf<br />a  g <br />t<br />Choose an equation<br />Plug in values to solve the problem <br />Example: <br />xf = xi + vit + 0.5at2  yf= yi+ vit + 0.5gt2<br />yf =0 + 0+ 0.5(-9.81)t2<br />yf at 1.00 s = -4.90 m<br />yf at 2.00 s = -19.6 m<br />yf at 3.00 s = -44.1 m<br />