 # Wed, 12/17 Question 12 on your bellringer sheet.

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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

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

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

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)

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

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

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

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)

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

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

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

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

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

#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

#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.

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

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