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A 19.2 kg person climbs up a uniform ladder
with negligible mass. The upper end of the
ladder rests on a frictionless wall. The bottom
of the ladder rests on a floor with a rough
surface where the coefficient of static friction
is 0.1 . The angle between the horizontal and
the ladder is θ . The person wants to climb
up the ladder a distance of 0.49 m along the
ladder from the ladder’s foot.
What is the minimum angle θmin (between
the horizontal and the ladder) so that the
person can reach a distance of 0.49 m without
having the ladder slip? The acceleration of
gravity is 9.8 m/s^2
Answer in units of â—¦

A 192 kg person climbs up a uniform ladder with negligible mass The upper end of the ladder rests on a frictionless wall The bottom of the ladder rests on a flo class=

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MathPhys

Answer:

63°

Explanation:

Draw a free body diagram of the ladder.  There are 4 forces:

Normal force N pushing up at the base of the ladder.

Friction force Nμ pushing right at the base of the ladder.

Weight force mg pushing down a distance x up the ladder.

Reaction force R pushing left at the top of the ladder.

Sum of forces in the x direction:

∑Fₓ = ma

Nμ − R = 0

R = Nμ

Sum of forces in the y direction:

∑Fᵧ = ma

N − mg = 0

N = mg

Sum of moments about the base of the ladder:

∑τ = Iα

R (L sin θ) − mg (x cos θ) = 0

R (L sin θ) = mg (x cos θ)

Substituting:

Nμ (L sin θ) = mg (x cos θ)

mgμ (L sin θ) = mg (x cos θ)

μ (L sin θ) = x cos θ

tan θ = x / (μL)

θ = atan(x / (μL))

Given x = 0.49 m, μ = 0.1, and L = 2.5 m:

θ = atan(0.49 m / (0.1 × 2.5 m))

θ ≈ 63°

To solve the problem we will first calculate the reaction and the normal force.

The angle of the ladder should be 63°.

Given to us

  • Distance the person wants to travel, x = 0.49 m,
  • the coefficient of static friction, μ = 0.1,
  • Length of the ladder, L = 2.5 m:

Free Body Diagram

  • There are 4 forces
  1. Reaction force R pushing left at the top of the ladder,
  2. Normal force N pushes up the ladder at the base of the ladder,
  3. Friction force Nμ pushing right at the base of the ladder,
  4. Weight force of the person pushing down = mg,

Sum of Vertical vector forces,

[tex]\sum F_y = 0\\N - mg = 0\\N = mg[/tex]

Sum of Horizontal vectors forces,

[tex]\sum F_x = 0\\N\mu - R = 0\\R = N\mu[/tex]

Sum of moments at the base of the ladder

[tex]R (L\ sin\theta) - mg (x\ cos\theta) = 0\\R (L\ sin\theta) = mg (x\ cos\theta)[/tex]

Substituting the values of R and N,

[tex]N\mu (L\ sin \theta) = mg (x\ cos \theta)\\mg\mu (L\ sin \theta) = mg (x\ cos\theta)\\\mu (L\ sin \theta) = x\ cos \theta\\tan \theta = \dfrac{x}{\mu L}\\\theta = tan^{-1}( \dfrac{x}{\mu L})[/tex]

Substituting the values,

[tex]\theta = tan^{-1}(\dfrac{0.49\ m}{0.1\times 2.5 m})\\\\\theta = tan^{-1} (0.96)\\\\\theta = 62.969^o \approx 63^o[/tex]

Hence, the angle of the ladder should be 63°.

Learn more about Friction:

https://brainly.com/question/13357196

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