The document uses a box named Billy and a table named Terry to explain free body diagrams. It provides an example of drawing a free body diagram for Billy, who has a mass of 5 kg and is pushed to the right by a 12 N force. Terry explains that the diagram would show Billy's weight as a 49 N force down, a normal force of 49 N up from the table, the 12 N applied force to the right, and a 12 N frictional force to the left to balance the forces since Billy is moving at a constant speed. The document then provides another example where Billy accelerates to the right due to forces.

1. Free Body Diagram
It’s Really Easy

2. HI
THERE! MY
I’M BILLY THE
NAME IS VINNIE
BOX!
THE VECTOR!
AND I’M TERRY THE
TABLE. TOGETHER WE
WILL TRY TO EXPLAIN THE
FREE BODY DIAGRAM

3. I AM MADE OF
MATTER, THEREFORE I
HAVE MASS
AND BECAUSE BILLY
HAS MASS, THE EARTH
PULLS HIM DOWN. WE
CALL THIS PULL
“WEIGHT”

4. I HAVE A
MASS OF 1O
KILOGRAMS. EVERYONE
SAYS I HAVE A REALLY
NICE MASS.
BECAUSE OF THE EARTH’S
GRAVITY, BILLY HAS WEIGHT.
THE WEIGHT IS A FORCE. EACH
KILOGRAM OF MASS HAS A
WEIGHT OF 9.8 NEWTONS.
BILLY WEIGHS 98 NEWTONS.

5. I WEIGH 98
NEWTONS!
I BECAUSE WEIGHT IS A
REPRESENT FORCE, WE USE VECTORS TO
BILLY’S WEIGHT. I SHOW THE FORCE. VECTORS
AM 98 NEWTONS HAVE 2 PARTS, SIZE AND
DOWN. DIRECTION.

6. I WEIGH 98
NEWTONS! NOW BILLY IS SITTING ON
ME. I AM HOLDING UP HIS
WEIGHT. I DO THIS WITH A
FORCE OF MY OWN. I CALL IT
A NORMAL FORCE.
I
REPRESENT
BILLY’S WEIGHT. I
AM 98 NEWTONS
DOWN.

7. NOTICE THAT THE
NORMAL FORCE IS EXACTLY
I THE SAME SIZE AS BILLY’S
REPRESENT THE WEIGHT. NOTICE ALSO THAT
NORMAL FORCE. I AM IT IS THE OPPOSITE IN
98 NEWTONS UP. DIRECTION.
IMPORTANT
THE TWO FORCES ARE
THE SAME SIZE AND
IN OPPOSITE
DIRECTIONS. BECAUSE
I OF THIS, THEY CANCEL
REPRESENT
BILLY’S WEIGHT. I EACH OTHER. WHEN
AM 98 NEWTONS FORCES CANCEL EACH
DOWN.
OTHER, THE NET
FORCE = 0 NEWTONS.

8. NOW WE WILL
WORK TOGETHER TO IT’S REALLY
SHOW SOME EASY. TRUST ME, I’M
EXAMPLES! A BOX
LET’S START WITH AN
EASY ONE....

9. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
I GET PUSHED
AROUND.
AND I HOLD
5 KG EVERYTHING UP...
I WILL BE SHOWING
THE FORCES.

10. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
BECAUSE I
HAVE A MASS OF 5
KG, I HAVE A WEIGHT OF BECAUSE
5 KG 49 NEWTONS. BILLY IS MOVING AT A
CONSTANT SPEED, THE
NET FORCE ON HIM
MUST BE ZERO.
I AM A
VECTOR THAT HAS A SIZE
OF 49 NEWTONS AND MY
DIRECTION IS DOWN

11. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
FIRST, WE PLACE BILLY
ON ME. I AM NOW FEELING
BILLY’S WEIGHT OF 49
NEWTONS.
5 KG
49 NEWTONS DOWN

12. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
49 NEWTONS UP
NEXT, IN ORDER TO
HOLD BILLY UP, I APPLY A
NORMAL FORCE. IT IS THE
SAME SIZE AS BILLY’S
WEIGHT.
5 KG
49 NEWTONS DOWN

13. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
49 NEWTONS UP
NOW WE APPLY THE 12
NEWTON FORCE PUSHING
BILLY TO THE RIGHT. THE
DIRECTION OF THE ARROW
12 NEWTONS IS THE THE DIRECTION OF
THE FORCE.
RIGHT
5 KG
49 NEWTONS DOWN

14. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
49 NEWTONS UP THIS IS
IMPORTANT! BECAUSE
BILLY MOVING AT A
CONSTANT SPEED, THE NET
FORCE ON HIM MUST BE
ZERO. THEREFORE,
12 NEWTONS SOMETHING MUST
BALANCE THE APPLIED
RIGHT FORCE.
5 KG
49 NEWTONS DOWN

15. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
49 NEWTONS UP
THAT FORCE IS
FRICTION. IT WORKS IN
THE OPPOSITE DIRECTION
THAT BILLY IS MOVING.
BECAUSE HE IS MOVING AT A
12 NEWTONS CONSTANT SPEED, THE
12 NEWTONS FRICTION IS THE SAME SIZE
RIGHT LEFT AS THE APPLIED FORCE.
5 KG
49 NEWTONS DOWN

16. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO MOVE AT A CONSTANT SPEED TO THE RIGHT. DRAW
THE FREE BODY DIAGRAM.
49 NEWTONS UP
BECAUSE ALL OF THE
FORCES ON BILLY ARE
BALANCED, THE NET FORCE
IS ZERO AND HE IS AT
12 NEWTONS 12 NEWTONS EQUILIBRIUM. LET’S TRY
RIGHT ANOTHER...
LEFT
5 KG
49 NEWTONS DOWN

17. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO ACCELERATE TO THE RIGHT. IF THE NET FORCE ON
BILLY IS 10 NEWTONS RIGHT, DRAW THE FREE BODY DIAGRAM.
49 NEWTONS UP
BILLY STILL WEIGHS THE
SAME, SO THE WEIGHT AND
NORMAL FORCES ARE THE
12 NEWTONS ? NEWTONS SAME. WHAT’S DIFFERENT?
RIGHT LEFT
5 KG
49 NEWTONS DOWN

18. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO ACCELERATE TO THE RIGHT. IF THE NET FORCE ON
BILLY IS 10 NEWTONS RIGHT, DRAW THE FREE BODY DIAGRAM.
49 NEWTONS UP
BECAUSE BILLY IS
ACCELERATING, THE NET
FORCE ON HIM CANNOT BE
ZERO. THE FORCE OF
FRICTION MUST BE SMALLER
12 NEWTONS ? NEWTONS THAN THE APPLIED FORCE.
RIGHT LEFT HOW MUCH SMALLER?
5 KG
49 NEWTONS DOWN

19. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO ACCELERATE TO THE RIGHT. IF THE NET FORCE ON
BILLY IS 10 NEWTONS RIGHT, DRAW THE FREE BODY DIAGRAM.
49 NEWTONS UP
IF WE ARE APPLYING A
12 NEWTON FORCE TO BILLY
AND YET THE NET FORCE IS
ONLY 10 NEWTONS, THERE IS
A DIFFERENCE OF 2
12 NEWTONS ? NEWTONS NEWTONS. THIS
RIGHT LEFT DIFFERENCE COMES FROM
5 KG FRICTION.
49 NEWTONS DOWN

20. BILLY THE BOX IS PLACED ON A FLAT SURFACE. BILLY HAS A MASS
OF 5 KILOGRAMS. A FORCE OF 12 NEWTONS IS APPLIED TO BILLY
CAUSING HIM TO ACCELERATE TO THE RIGHT. IF THE NET FORCE ON
BILLY IS 10 NEWTONS RIGHT, DRAW THE FREE BODY DIAGRAM.
49 NEWTONS UP
IN ORDER FOR ALL THIS TO
WORK, THE FORCE OF
FRICTION MUST BE 2
NEWTONS TO THE LEFT.
12 NEWTONS 2 NEWTONS HOPE THIS HELPS.
RIGHT LEFT
5 KG
49 NEWTONS DOWN