# What is projectile motion? - R

What is Projectile Motion?
By: Brett A., 2012

1.) Projectile Motion Itself:
Projectile motion is the study of how objects fly through the air at different angles and how they will land. Many variables act along with projectile motion. Three of the most important variables include gravity, the horizontal force of the object, and air resistance. These three variables are very important to the flight of an object. They determine the length, speed, bounce, and several more parts of flying through the air. We will cover those later in the next chapter, but for now you should hear the basics. An angle of motion is made up of two different things, gravity and the horizontal motion. You may not realize it but every time you throw something it has a degree of angle, correct? If you thought more clearly you would see that everything moving in the air has an angle of movement. This does not include birds and planes and
 Figure 1
such because they have a way of staying up there. However, if they fell out of the sky they too would be following an angle. The higher the angle or the lower the angle makes it change its path of flight. Studies show that a 45 degree angle makes an object travel further than other angles. Angles other than 45 degrees would go too high or too low and 45 degrees still can go further when bounce is involved. The lower the ball is thrown or hit the more it will skip and the higher it is hit the less it will bounce. So now that you know the basics, let’s go into the variables.

2.)The Complications and Variables of Projectile Motion:
Several things contribute to projectile motion’s concept. Air resistance, gravity, and the horizontal power of the object in the air all have a large amount of effect on the object’s flight. While in the air, the horizontal motion of the object pushes it forward while the force of gravity pulls it down and the wind pulls the object whichever way it is blowing. Wind will always be changing and you cannot count on it to stay the same and the speed and direction of the wind will vary forever. How heavy an object is will also affect the flight. The object will be affected more or less by the wind depending on the weight and the heavier the object the less affected it would be. Gravity pulls objects down at the same rate all the time on Earth so you do not have to worry about that changing. However, with horizontal motion, the force used to launch an item will significantly change the distance it will travel. A person must have a vague idea of how much power to put on the object, depending on the object’s weight, in order to control where they want to let it fall.

3.) The History of Projectile Motion:
In the days of Galileo, (A great Italian astronomer known for other things as well, who lived from 1564-1642.) people believed a theory called impetus that was their theory of items flung into the air. They thought that an objects flight depended on the power behind the object, or force. When they threw or shot something they thought the projectile would keep moving until it had no power left, or lost its impetus, as they thought. It would then fall straight down as shown in the diagram. A man named Niccolo Tartaglia noticed that this was not correct and by just observing more carefully he noticed that objects actually followed a curved path
 Figure 2

 Figure 1

instead of going in just a straight line and then stopping. He also noticed how it had a gradual slope to the ground different from the abrupt plummeting of action they had believed in past years. Galileo extended on Tartaglia’s idea and he discovered that the path of a projectile happened to curve because of two forces that joined together rather than one. The two forces he noticed, ironically, were gravity and horizontal motion. After that Galileo called any angle of flight a parabola and every object had a parabola when it went through the air.

4.) Conclusion
Projectile motion is the study of the flight of objects and the flight of objects, as I hope this writing summarized that. It also showed that several different variables changed the flight of an object. In the last chapter it talked about the history of how projectile motion was found out and what it was before. So, hopefully you learned something!

Glossary:

Gravity: Gravity is the pull of an object on another. All objects have a pull, all too small except Earth and other planets to take effect though.

Horizontal motion: The speed at which an object moves.

Impetus: Impetus is what people believed before the parabola was discovered, they thought an object would fly until it lost power, then it would simply fall. They called this
impetus.

Parabola: The parabola is the curved path of a projectile, or the angle it follows.

Air Resistance: The force of wind going against a flying object.

Citations:
Website: http://library.thinkquest.org/2779/
One book: Title: Conceptual Physics Tenth Edition Author: Paul G. Hewitt Published: San Francisco: Pearson Addison Wesley, c2006.
Second book: Title: Motion, forces, and energy Author: Peter Kahan Published: Needham, Mass.: Prentice Hall, 2000.
Database: http://school.eb.com/all/comptons/article-204449?query=projectile%20motion&ct=null
Picture: http://media.wiley.com/Lux/24/10024.nfg012.jpg