- #1
Tyler Riley
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Hello! I am an AP Physics student and had a quick question for validity. I was prompted with this question in class today:
Example 7: An 8-meter ladder of weight 355 N leans at an angle of 50° to the floor against a smooth vertical wall. Assume the center of weight (gravity) for the ladder is at its linear center. Find the force exerted by the wall and the floor upon the ladder and the friction between the floor and the ladder.
I wasn't really paying attention and missed a class day of notes so I really don't understand anything really and was hoping you could answer my few questions.
Here is what I copied:
f = floor
r = lever arm
Ff = Friction force
Nf = Normal force or Floor
W⊥ = Weight
Nw = Normal force of Wall
rL = (4m)cos(50) = 2.57m
rW = (8m)sin(50) = 6.13m
∑Fy = 0
Nf - W⊥ = 0
Nf = W⊥
355 N = 355 N
∑Fx = 0
Ff - Nw = 0
∑τ = 0
-W⊥ * rL - Nw * rW = 0
(-355 N) * (2.57) - Nw * (6.13) = 0
-912.35 = Nw * (6.13)
Nw = -148.833
Here are my questions:
Why isn't it (4m)sin(50) instead of (8m)sin(50)?
And why does she plug in
-W⊥
in
-W⊥ * rL - Nw * rW = 0
instead of
Nf * μ
in
Nf * μ * rL - Nw * rW = 0
Example 7: An 8-meter ladder of weight 355 N leans at an angle of 50° to the floor against a smooth vertical wall. Assume the center of weight (gravity) for the ladder is at its linear center. Find the force exerted by the wall and the floor upon the ladder and the friction between the floor and the ladder.
I wasn't really paying attention and missed a class day of notes so I really don't understand anything really and was hoping you could answer my few questions.
Here is what I copied:
f = floor
r = lever arm
Ff = Friction force
Nf = Normal force or Floor
W⊥ = Weight
Nw = Normal force of Wall
rL = (4m)cos(50) = 2.57m
rW = (8m)sin(50) = 6.13m
∑Fy = 0
Nf - W⊥ = 0
Nf = W⊥
355 N = 355 N
∑Fx = 0
Ff - Nw = 0
∑τ = 0
-W⊥ * rL - Nw * rW = 0
(-355 N) * (2.57) - Nw * (6.13) = 0
-912.35 = Nw * (6.13)
Nw = -148.833
Here are my questions:
Why isn't it (4m)sin(50) instead of (8m)sin(50)?
And why does she plug in
-W⊥
in
-W⊥ * rL - Nw * rW = 0
instead of
Nf * μ
in
Nf * μ * rL - Nw * rW = 0