Key concepts
Physics
Motion
Gravity
Resistance
Angles

Introduction
Have you ever seen a long, game-winning pass in a football game, a baseball player throw in a ball from way out in the outfield or a soccer goalie punt a ball all the way down the field? All of these actions involve a player trying to throw or kick a ball as far as possible. There is some science behind these throws and kicks. And sometimes it is all about the angle. The angle can affect just how far a throw or a kick can carry a ball. Should you make a shallow throw (straight out, parallel to the ground), a steep throw (throwing the ball high up in the air) or something in between? Try this sports science project to find out!

Background
An object that is thrown, kicked or otherwise launched through the air is called a projectile. The study of how projectiles move through the air is called projectile motion. When a projectile is launched, it has an initial velocity (its speed and direction of motion). When a projectile is moving through the air, however, it is subject to the force of gravity, which causes it to move down toward Earth. It is also subject to the force of air resistance, which slows the projectile down.

When air resistance is very low, a projectile moves in the shape of a parabola—a type of mathematical curve. (You can do an Internet search for "parabola" to see what one looks like.) The path the ball follows (called its trajectory) will determine how far it goes before it hits the ground. Adjusting the ball’s initial angle and keeping its initial speed constant is one way to find out the best angle to throw a ball as far as possible. In this experiment you will throw a ball as hard as you can while changing the ball's initial angle relative to the ground. What angle do you think will make the ball go the farthest?

Materials

• Sports ball of your choice (baseball, tennis ball, football, etcetera)
• Large open area to throw the ball
• Three each of three different objects to mark where the ball lands on the ground (for example, three sticks, three rocks and three golf balls)
• Helper

Preparation

• Make sure you have a large, open area to throw, and that there are no other people or objects in the way.
• Do some stretching or warm-up exercises before you start the experiment—it will involve a lot of throwing!
• Pick a place to stand in your large, open area. Mark a place on the ground so you know to always throw the ball from that location.
• Pick a direction to throw your ball. (If it is a windy day, make sure you pick a consistent direction relative to the wind.)
• What type of angle do you think will get the farthest distance—shallow, steep or medium?

Procedure

• Throw your ball as hard as you can, relatively straight forward at a "shallow" angle—as parallel to the ground as you can. If you are familiar with measuring angles in degrees, imagine trying to throw the ball at about a 15-degree angle relative to the ground. Can you think of a time this type of throw would be best?
• Have your helper mark where the ball lands (for example, with a rock).
• Repeat the throw at that angle two more times. Try to consistently throw the ball as hard as you can, so its initial speed is constant. Have your volunteer mark each through. Why do you think it's important to perform the same test at least a few times?
• Now repeat the procedure for a "medium" angle (outward and upward) of about 45 degrees three times. Remember to try and consistently throw the ball as hard as possible. Use a different marker object for where these throws land. How did this distance compare with the shallow angle?
• Now, do the same for a "steep" angle (up in the air and slightly forward but not straight up) of about 75 degrees. How do you think this throw distance will compare with the others? Remember to try and consistently throw the ball as hard as possible. Use another different type of marker for this batch of throws.
• Now, analyze the results of your experiment by looking at the markers. Which throws went farthest? What angle do you think is best if you want to throw the ball as far as possible?
• Extra: Try the experiment using different types of balls. How do you think the ball size, weight and shape will affect what angle is best to throw the farthest? Did you get different results?
• Extra: Repeat the exercise, this time kicking a ball instead. Do you think the angles will yield relatively similar distances? Did you get different results than when you threw the ball?

Observations and results
In most cases you should see that a medium, 45-degree angle made the ball go the farthest. When you throw the ball at a very shallow angle, gravity pulls it down and the ground is closer, which ends the throw sooner so it does not have as much time to travel as far forward. When you throw the ball at a very steep angle, most of its velocity is directed upward instead of forward, so it does not make much forward progress.

Depending on the type of ball and the amount of air resistance on it, however, you might see different results. A ball that has a lot of air resistance (such as a whiffle ball) might slow down significantly when it is in the air for a long time, so it might actually go farther at a shallower angle.

More to explore
How Far Can You Throw (or Kick) a Ball?, from Science Buddies
Projectile Motion, from the Physics Classroom
Science Activities for All Ages!, from Science Buddies

This activity brought to you in partnership with Science Buddies