Free Falling Bodies by gjjur4356

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									                  Free Falling Bodies

Aristotle [384BC – 322BC]


The larger the mass, the greater the speed [e.g. a 20 kg
body falls twice as fast as a 10kg body


He never performed experiments to validate any of his
theories


His views went unchallenged for almost 2000 years
Galileo Galilei [1564 – 1642]

experiment……………consider a heavy mass
attached to a lighter mass, falling to earth
                                                    Light body
1.   The light body falls slower, slowing
       the heavy body. The combined
       mass falls slower than the heavy                  Heavy body
       mass alone.
2.   The combined mass is heavier than
       the heavy mass alone. The
       combined mass falls faster than
       the heavy mass alone.

3.   We have a PARADOX [two different outcomes]. Therefore
     the basic premise is incorrect. Heavy bodies can NOT fall
     faster than lighter ones.
                   Free Falling Bodies
 A free-falling object is an object which is falling under the
  sole influence of gravity.

 Any object which is being acted upon by only the force of
  gravity is said to be in a state of free fall.

 There are two important motion characteristics which are true
  of free-falling objects:

   1. Free-falling objects do not encounter air resistance.

   2. All free-falling objects (on Earth) accelerate downwards at
      a rate of 9.8 m/s/s
Summary – Galileo

 All falling bodies accelerate towards the earth

 All falling bodies, regardless of mass, experience the same
  acceleration

 This special acceleration due to gravity is given symbol 'g'

 g = 9.8 m/s2 [down] or -9.8 m/s2

 for all problems involving freely falling bodies, whether
  they are moving up, or down, or at rest at the maximum
  height, use
                       a = -9.8 m/s        2
Sample problem 1 : A Dinosaur falls into a crater left by a large
meteorite. It takes the Dinosaur 6.7 seconds to hit the bottom,
How deep is the crater ?
Sample Problem 2:

A ball is thrown upwards at
22 m/s [UP] at t=0s.

Find:
1.   Its velocity at t = 1.5 s
2.   The time it requires to reach maximum height
3.   The maximum height reached
4.   Its displacement during the first
     1.8 s of its flight
              Homework
• Pg 66 5,6,7,8,9

								
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