1. Wed, 12/17 Question 12 on your bellringer sheet.
I am collecting these today!!!!!!
TO DO TODAY:
Review Yesterday
Continue Forces/Newton
Practice problems with Equilibrium
FBDs and Net Force problems

2. Free Body Diagram Shows all forces (vector) acting on an object
Unit for force = N (Newton)
FN = 500 N
Fp = 1000 N
Ff = 200 N
Fg = 500 N

3. Common Forces Fg = weight  downward
FN = normal  perpendicular to surface
Ff = friction (includes air)  opposite to motion
Fp = push/pull
FT = tension in string
FRICTION FN
FRICTION Fg

4. ΣF = (summation) net force
Vector sum of all forces on an object
ΣF = (summation) net force
x and y components:
F(x) = F·cos θ
F(y) = F·sin θ
Fp(y) Fp θ
Fp(x)

5. In-Class Problem #1
A 9 N book sits at rest on a table. ΣF = 0 N

6. Practice… Draw a free body diagram for the following:
A pen is pushed to the left on a table.
Fnorm
Fpush
Ffric
Fgrav

7. Pushing a book across the table
Fnorm = Going Up
Fappl = You pushing
Fgravity = The weight of the object and gravity’s pull
Ffriction = Friction

8. Things to keep in mind… They will NOT always have 4 arrows.
“System” can be shown as a box or a dot. (Here it will be shown as a box to make it easier to see)

9. #1 A book is at rest on a tabletop
Only Fnorm and Fgrav are acting on the book while it sits

10. Suspended? Ftens and Fgrav
#2 A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder.
Suspended?
Ftens and Fgrav

11. #3 A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity.
Falling and considering air resistance? Fair

12. Free Fall, neglect air resistance?
#4 An egg is free-falling from a nest in a tree. Neglect air resistance.
Free Fall, neglect air resistance?
Only force is Fgrav

13. #5 A girl is suspended motionless from the ceiling by two ropes.
Something hung?
No Fnorm
Ftens
(Tension)

14. #6 A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance

15. #7 A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance.

16. #8 A skydiver is descending with a constant velocity
#8 A skydiver is descending with a constant velocity. Consider air resistance.

17. #9 A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration.