1. Galileo and Speed
May 21, 2014

2. Objectives
1. Explain the Galileo’s concept of inertia
2. Distinguish between speed and
velocity
3. Perform calculations involving speed,
time, and distance

3. Aristotle
 Natural motion – at rest
 Unatural motion– force
required by human or
animal
 Force = push or pull

4. Galileo
 1500’s – Leaning Tower
of Pisa
 Force required to
start an object,
but not to keep it
moving

6.  if friction was absent the ball would move forever
 All objects show the same properties as the
rolling balls
 Inertia – property of objects and their motion

7.  Speed – Fast or slow?
 Galileo – first to measure speed
 Speed = distance/time

8.  Horse covers 40 kilometers in 2 hr
 20 km/hr
 You run 3 meters in 0.5 s
 6 m/s
 Average speed – total distance and time
 Instantaneous speed – speed at any given moment
 Constant speed – doesn’t slow down or speed up

9.  What is the average speed of a cheetah that
sprints 100m in 4s? How about 50m in 2s?
 The speedometer on a bicycle moving east
reads 50 km/h. What distance will it cover in
2 hours?

10. Relative Motion
 Everything is moving
Motion is always relative to something
else
 Unless otherwise specified we talk about
motion relative to the earth