Name: ____________________________ Date: ______________ Block: _____
How the Physics of Football Works
by Craig C. Freudenrich, Ph.D.
Source: www.howstuffworks.com
When you throw a football across the yard to your friend, you are using physics. You make
adjustments for all the factors, such as distance, wind and the weight of the ball. The farther away
your friend is, the harder you have to throw the ball, or the steeper the angle of your throw. This
adjustment is done in your head, and it's physics -- you just don't call it that because it comes so
naturally.
Physics is the branch of science that deals with the physical world. The branch of physics that is
most relevant to football is mechanics, the study of motion and its causes. We will look at
three broad categories of motion as they apply to the game:



Delivery of a football through the air
Runners on the field
Stopping runners on the field
Watching a weekend football game could be teaching you something other than who threw the
most passes or gained the most yards. Football provides some great examples of the basic
concepts of physics -- it's present in the flight of the ball, the motion of the players and the force
of the tackles.
Throwing the Football
When the football travels through the air, it always follows a curved, or parabolic, path because
the movement of the ball in the vertical direction is influenced by the force of gravity. As the ball
travels up, gravity slows it down until it stops briefly at its peak height; the ball then comes down,
and gravity accelerates it until it hits the ground. This is the path of any object that is launched or
thrown (football, arrow, ballistic missile) and is called projectile motion. To learn about projectile
motion as it applies to football, let's examine a punt (Figure 1). When a punter kicks a football, he
can control three factors:



The velocity or speed at which the ball leaves his foot
The angle of the kick
The rotation of the football
The rotation of the ball -- spiral or end-over-end -- will influence how the ball slows down in flight,
because the ball is affected by air drag. A spiraling kick will have less air drag, will not slow down
as much and will be able to stay in the air longer and go farther than an end-over-end kick. The
velocity of the ball and the angle of the kick are the major factors that determine:



How long the ball will remain in the air (hang-time)
How high the ball will go
How far the ball will go
The angle of a kick helps determine how far it will travel.
Name: ____________________________ Date: ______________ Block: _____
When the ball leaves the punter's foot, it is moving with a given velocity (speed plus angle of
direction) depending upon the force with which he kicks the ball. The ball moves in two
directions, horizontally and vertically. Because the ball was launched at an angle, the velocity
is divided into two pieces: a horizontal component and a vertical component. How fast the
ball goes in the horizontal direction and how fast the ball goes in the vertical direction depend
upon the angle of the kick. If the ball is kicked at a steep angle, then it will have more velocity
in the vertical direction than in the horizontal direction -- the ball will go high, have a long
hang-time, but travel a short distance. But if the ball is kicked at a shallow angle, it will have
more velocity in the horizontal direction than in the vertical direction -- the ball will not go very
high, will have a short hang-time, but will travel a far distance. The punter must decide on the
best angle in view of his field position. These same factors influence a pass or field goal.
However, a field goal kicker has a more difficult job because the ball often reaches its peak
height before it reaches the uprights.
Runners on the Field
When we look at runners on the field, several aspects can be considered:



Where they line up for a play
Changing directions
Running in an open field
Line-Up Positions
When we look at the positions of the backs, both offensive and defensive, we see that they
typically line up away from the line of scrimmage on either side of the offensive and
defensive linemen. Their positioning allows them room, or time, to accelerate from a state of
rest and reach a high speed, to either run with the ball or pursue the ball carrier. Notice that
the linebackers have far more room to accelerate than the linemen, and the wide receivers
have far more room than the linebackers. So linebackers can reach higher speeds than
linemen, and wide receivers can reach the highest speeds of all.
Running in an Open Field
When running in an open field, the player can reach his maximum momentum. Because
momentum is the product of mass and velocity, it is possible for players of different masses
to have the same momentum. For example, our running back would have the following
momentum (p):

p = mv = (98 kg)(9.8 m/s) = 960 kg-m/s
For a 125 kg (275 lb) lineman to have the same momentum, he would have to move with a
speed of 7.7 m/s. Momentum is important for stopping (tackling, blocking) runners on the
field.
We have only touched on some of the applications of physics as they relate to football.
Remember, this knowledge appears to be instinctive; most often, players and coaches don't
consciously translate the mechanics of physics into their playing of the sport. But by making
that translation, we can understand and appreciate even more just how amazing some of the
physical feats on the football field really are. Also, applying physics to football leads to better
and safer equipment, affects the rules of the sport, improves athletic performance, and
enhances our connection to the game.
Name: ____________________________ Date: ______________ Block: _____
Journal Entry
According to Newton’s second law that states force = mass x acceleration
(neglecting air resistance), and from the article “How the Physics of Football
Work” please describe what factors influence the force that a player throws a
football and explain why.
Please write your response in complete, grammatically correct sentences.
Responses should be minimally eight (8) sentences.
Name: ____________________________ Date: ______________ Block: _____
Football Challenge A
Learning Objective: To explore the relationship between football and the physical
science concepts of velocity, acceleration, and force
Goal: To throw a ball with the force of 0.85N
Key Words: acceleration, force, Newton’s second law, momentum, and velocity
Materials needed:
Football*
Data sheet*
Stopwatch*
Calculator*
Tape measure*
Balance
*Make sure you have all of these materials before going outside
Directions:
Your team will receive three attempts to throw a football with a force of 0.85N.
Collect and calculate all the data in the data collection chart. Calculate the force
after each attempt to determine strategy of which factors to change. Be sure to
record what factors you adjusted after each attempt. The team that comes
closest to the target force will be rewarded.
Teams:
Each team will consist of the following roles:
1. Thrower: responsible for throwing the ball according to the factors set
by the team
2. Time Keeper: responsible for using the stop watch to record the ball
spent in the air (from the hand of the thrower until it hits the ground)
3. Distance Monitor: responsible for marking where the football hit the
ground and measuring that distance with the tape measure
4. Recorder: responsible for recording all the data reported by the
timekeeper and distance monitor
5. Supervisor/helper: responsible for keeping the team on task and
providing assistance to all other team members
Name: ____________________________ Date: ______________ Block: _____
Data Sheet
Mass of football= ____________ kg
Attempt
Distance
Time
Factors Changed
1
2
3
Calculations:
Attempt
Initial
Velocity, Vi
Final
Velocity,
Vf
Initial Time,
to
Final Time, tf
1
2
3
Attempt
Acceleration, a
1
2
3
Force, F
Momentum, p
Name: ____________________________ Date: ______________ Block: _____
Football Challenge B
Directions: Follow the sequence of the football game and answer the physics- related
questions based on the information given in the NCAA football data table and in the problem
statements. Remember that all of the problems are connected to each other.
Length of field:
Width of field:
Height of goal posts:
Height of crossbar:
Width of goal posts (above
crossbar):
Length of ball:
Circumference of ball:
Mass of ball:
FOOTBALL (NCAA) Data Table
120 yards (including 10 yards of end zone at each end).
53 1/3 yards (160 feet).
At least 30 feet.
10 feet.
18 feet 6 inches, inside to inside.
10 7/8 to 11 7/16 inches (long axis).
20 3/4 to 21 1/4 inches (middle); 27 3/4 to 28 ½ inches (long
axis).
0.41 kg
1. It is the conference championship football game between the Redan Raiders and the
Lithonia Bulldogs. There is 2:00 left on clock in the fourth quarter, and it is 4th down for the
Raiders with 20 yards to go. The Raiders are up only by one touchdown so they want to
make sure that the Bulldogs don’t have a chance to tie the game. Therefore, they decide to
punt the ball. To be safe the coach wants the ball to be punted at least to their 10 yard line. If
the current line of scrimmage is at the 30 yard line, what will be the speed of the ball if
it has a hang time of 45 seconds?
2. The Raiders punted the ball pass the 10 yard line all the way into the inzone. The Bulldogs
recover the ball at the far end of the inzone with hopes to make a touchdown in the 55
seconds remaining in the game. If the player has a mass of 95kg, what must be his
speed and acceleration to make a touchdown for his team by the end of the game?
3. The star Raider linebacker knows that he has to gain the same momentum as the Bulldog
receiver if he has any hope of catching and tackling him. However, the Raider linebacker
only has a mass of 88kg. At what speed must the Raider linebacker run to gain the
same momentum as the Bulldog receiver?
4. The Raider defense failed to stop the determined Bulldog receiver from reaching the
inzone and getting a touchdown, and now it is a one-point game. The ball has two be placed
on the 2-yard line after a touchdown, where the scoring team has the option of going for the
extra point or the two-point conversion. The Bulldogs decide to play it safe and go for the
field goal to tie the game. The kicker kicks the ball with a force of 10N, what acceleration
must the ball achieve to maintain that force?
Eventhough, the bulldog kicker used enough force to kick the ball past the goal posts, he
forgot to factor in that it was a very windy night due to Hurricane Ivan’s approach. The wind
added so much air resistance that the ball went slightly to the left of the goal posts, and the
Redan Raiders WIN the conference championship!!
Name: ____________________________ Date: ______________ Block: _____
Word Problem Strategy
What is the question?
What equation(s) will I use?
What is the essential information?
Does my answer make sense?
What information is not needed?
Can I draw a diagram of the problem?
Solution:
Word Problem Strategy
What is the question?
What equation(s) will I use?
What is the essential information?
Does my answer make sense?
What information is not needed?
Can I draw a diagram of the problem?
Solution:
Name: ____________________________ Date: ______________ Block: _____