PES 100 

 Fall 2000

Physics in Everyday Life

Lecture Notes

Falling Balls

Read Chapter 1, Section 1.1

Falling Balls:

Now we will examine the acceleration, velocity and position of a simple system

[Drop ball]

Acceleration ? = g = 9.8 m/s2 = constant

Velocity:

initial velocity = 0

speeds up

follows straight line toward Earth

Results:

  • velocity keeps increasing with time
  • would move even faster if I threw it down

Mathematically: velocity = initial velocity + acceleration x time

Note: velocity does NOT depend on mass

Position of falling ball:

[Drop balls from different heights]

Will the higher one ever catch up with the lower one ?

"catch up" = be at the same height at the same time

[Drop from same height - different times]

Will the early one ever catch up with the late one ?

[Drop from same height - different times - different initial velocity]

Will later one catch up now ? maybe

 

From these experiments and our observations:

position (height) at some time depends on:
  • initial position
  • initial velocity
  • acceleration (often constant)
  • time
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