Purpose

1
Purpose

• Learn to collect and analyze data in a scientific
  manner.
• Apply what you have learned in the homework
• - Significant figures and uncertainties.
• - Statistical Concepts.
• Keep this purpose in mind as you do the lab
  activity
• You will be graded based on how well you apply
  these principles in the analysis of this
  projectile motion lab.

2
Projectile Motion

• Superposition of horizontal and vertical motion
• Horizontal motion Constant velocity (initial
  x-position set to zero for simplicity)
• x(t) vo cos q t
• Vertical motion Constant acceleration
• y(t) yo vo sin q t - 1/2 g t2

3
Projectile Motion

• Eliminating time t
• Solve horizontal equation for t t x(t) / (vo
  cos q)
• Plug this expression into vertical equation to
  replace t
• You obtain one single equation that describes
  mathematically the shape of the flight path
• y(t) as a function of x(t)
• y(t) yo vosin q x(t) / (vo cos q)- 1/2
  gx(t) / (vo cos q)2

4
Projectile Motion

• Flight path equation can be solved for initial
  velocity (see homework)
• ? Any pair x(t), y(t) (any point of the flight
  path) can in principle be used to calculate the
  initial velocity. We will use the endpoint (where
  ball hits the floor) because it is relatively
  easy to measure.
• You also need to measure yo and q

5
Equipment

• Projectile motion launcher
• - Do not aim launcher at people.
• - Wear goggles to protect your eyes.
• - Load the metal ball into the correct end of
  the launcher
• The end that has the photogate attached to
  it.

6
Using Graphical Analysis for Windows (GAW/GAX)

• This program is found here
• C\Labware\Programs\Gax\Gax.exe
• There is also a shortcut on the desktop.
• Double click on Gax.exe or on the shortcut on
  the desktop to launch the program.

7
Write x and y data into columns ? Graph appears
8
Double click on graph points to get Graph
Options Window. (select error bars, remove
connecting lines etc.)
9
Changing the error bars Click on x or y box
on top of data columns to get Column Options
Window (next slide).
10
Column Options window Select size of error
bars, change name of column, etc.
11

• Curve Fitting
• Select data with cursor in graph window (draw a
  box around them)
• Click on Analyze menu.

12
Select Automatic Curve Fit, then select the
type of fit.
13
(No Transcript)