3. EXPERIMENTAL TECHNIQUES AND METHODS
Experiment 1. Projectile Motion
Experiment 2. Projectile Motion Using Photogates
Experiment 3. Projectile Range Versus Angle
4. EXPERIMENTAL DATA AND ANALYSIS
4.1 Projectile Motion – Part A
4.2 Projectile Motion – Part B
4.4 Projectile Motion Using Photogates– Part B
We concluded that (1) the height is not measured correctly, (4) the air friction, and (5) some other reasons can make the experimental values to be different from the accepted values. We used a normal ruler to measure distances in the experiment, and it obviously can trigger some errors in the values, and yet we think this is not the main reason why experimental values are quite different from the expected ones. Maybe the air resistance is the main source of the errors in values. In the textbook of the general physics class, it says air friction can lessen the distance of flight to half time to time. The ball fired had initial speed of about 6~7m/sec, and this is large enough to get big resistance from the air. Not only the air resistance is making error, but also the slanted launcher is either. When the launcher is slanted and the ball has to be triggered to the back of the launcher, the ball is lowered. So, to lift the ball to the hole of the launcher, energy is consumed and the initial velocity of the ball must be slower than when it’s not slanted.
In summary, we think the air resistance is the main source of the error, but inaccurate measuring tools, and the energy waste for raising the ball in the launcher also can make some differenced to the values we got from the expected ones.
 Holliday Rensick Walker, Fundamental of Physics 8ed. John Wiley & Sons 2009