Motion & Acceleration

Did Galileo test his theory from the Leaning Tower of Pisa?
- Unlikely
  - height ~ 10 stories (see Seeds) => fall time 2-3 sec
  - therefore speed 40-60 mph, and friction definitely important
- Lunar Astronaut David Scott, in 1971, dropped a feather and a hammer at the same time -- they fell together (no air friction!)
Galileo reasoned further, based on observations of balls rolling on inclined planes:
- downward slant -- ball accelerates
- upward slant -- ball deccelerates demo
- therefore flat -- ball would roll with constant velocity!
- This is the important first statement of the law of inertia -- i.e. that in the absence of forces, an object will move in a straight line with constant velocity.
  - Revolutionary change from Greek thought
  - Lead to Newtons laws of motion and law of gravity