04-02 Galileo's 2D Experiment

• 0:00 - 0:06
How did Galileo quantify motion in 2 dimensions? Well, he was a good scientist so he did an experiment.
• 0:06 - 0:11
This experiment involved rolling balls off of a the table and controlling
• 0:11 - 0:15
the speed with which they rolled off the table and measuring where the ball landed.
• 0:15 - 0:20
Galileo controlled the speed of the ball by adjusting the height from which it rolled.
• 0:20 - 0:23
If he wanted it to go faster, he will roll it from higher up.
• 0:23 - 0:26
We'll talk later about how exactly he can know where to put the ball.
• 0:26 - 0:31
Galileo controlled the speed of the ball by adjusting where in the plane he released it from.
• 0:31 - 0:35
Higher up of course meant it would be going faster by the time it got to the edge of the table.
• 0:35 - 0:37
Like in his previous experiments, he didn't know
• 0:37 - 0:40
the units of his velocity, but he knew their relative sizes.
• 0:40 - 0:44
For example, he knew he can make the velocity twice as big as it was originally
• 0:44 - 0:47
or three or four times bigger and look what he found.
• 0:47 - 0:50
Again these are unit list distances but look at this correspondence.
• 0:50 - 0:55
When the ball had a velocity of 1 unit, represented here, the trajectory looks something
• 0:55 - 1:00
like this. With a velocity of 2 units, the ball went twice as far.
• 1:00 - 1:04
Likewise with 3 and 4 units of initial horizontal velocity.
• 1:04 - 1:09
Galileo called this Vx. This x indicates an x direction.
• 1:09 - 1:13
When we label axis, we usually called the horizontal direction x and the vertical y
• 1:13 - 1:18
and so this x is just here to remind us that we're talking about a velocity in the horizontal direction.
• 1:18 - 1:23
Okay, this is pretty interesting. What's the conclusion that we can draw from this data?
• 1:23 - 1:27
Is it that the horizontal velocity is equal to the motion in the x direction?
• 1:27 - 1:30
That horizontal velocity is somehow proportional to the motion in the x direction?
• 1:30 - 1:34
Or that horizontal velocity and x direction motion are totally unrelated?
• 1:34 -
Title:
04-02 Galileo's 2D Experiment
Video Language:
English
Team:
Udacity
Project:
PH100 - Intro to Physics
Duration:
01:36