Respuesta :
Answer:
0.8024
Explanation:
From the given question; we can say that the angular momentum of the system is conserved if the net torque is is zero.
So; [tex]I_o \omega _o = I_2 \omega_2[/tex]
At the closest distance ; the friction is :
[tex]f_s = \mu_s (mg)[/tex]
According to Newton's Law:
F = ma
F = mrω²
From conservation of momentum:
[tex]I_o \omega _o = I_2 \omega_2[/tex]
[tex]\omega_2= \frac { I_o \omega _o}{ I_2 }[/tex]
[tex]\omega_2=( \frac { I_1+ mr_o^2}{ I_1 + mr^2 })* \omega_o[/tex]
However ; since the static friction is producing the centripetal force :
[tex]\mu_s (mg) = mr \omega_2^2[/tex]
[tex]\mu _s = \frac{ \omega^2_2 *r }{g}[/tex]
The coefficient of static friction between the bottoms of your feet and the surface of the turntable can now be calculated by using the formula :
[tex]\mu _s = \frac{ \omega^2_2 *r }{g}[/tex]
= [tex]( \frac { I_1+ mr_o^2}{ I_1 + mr^2 })^2 * \frac{ \omega^2_o *r }{g}[/tex]
= [tex][\frac{1200+(73(6)^2)}{((1200)+(73)(3)^2)} ]^2*[\frac{(\frac{\pi}{4})^2(3)} {9.8}][/tex]
= 0.8024
The friction force between the bottom of the feet and the surface of the
turntable balance the centrifugal force due to rotation.
- The coefficient static friction is approximately 0.802
Reasons:
Radius of the turntable, r₀ = 6.00 m
The period of rotation of the turntable, T₀ = 8.00s
Moment of inertia of the turntable, [tex]I_t[/tex] = 1,200 kg·m²
Mass of the person, m = 73.0 kg
The point at which the feet starts to slip, r₁ = 3.00 m
Required:
The friction between the bottom of the feet and the surface of the turntable.
Solution:
The moment of inertia of the person and the turntable combined, J, can be
found by considering the person as a point mass.
Therefore;
At the rim, J₀ = [tex]I_t[/tex] + m·r² = 1,200 + 73×6² = 3828
J₀ = 3,828 kg·m²
At 3.00 m from the center, J₁ = [tex]I_t[/tex] + m·r² = 1,200 + 73×3² = 1,857
J₁ = 1,857 kg·m²
Angular momentum, L = J·ω
Whereby the angular momentum is conserved, we have;
L₀ = L₁
J₀·ω₀ = J₁·ω₁
[tex]\displaystyle \omega_1 = \mathbf{ \frac{J_0 \cdot \omega_0}{J_1}}[/tex]
Which gives;
To remain at equilibrium, the friction force, [tex]F_f[/tex] = The centrifugal force, [tex]F_c[/tex]
- [tex]F_f =\mu_s \cdot W = \mu_s \cdot m \cdot g[/tex]
[tex]\displaystyle F_c = \frac{m \cdot v^2}{r} = \frac{m \cdot (\omega \cdot r)^2}{r} = m \cdot r \cdot \omega^2[/tex]
Where;
[tex]\mu_s[/tex] = The coefficient of static friction
g = Acceleration due to gravity which is approximately 9.81 m/s²
r = The radius of rotation
ω = The angular speed
- [tex]F_f[/tex] = [tex]F_c[/tex]
Therefore;
- [tex]\displaystyle F_f = \mu_s \cdot m \cdot g = \mathbf{m \cdot r \cdot \omega^2}[/tex]
Therefore, at 3.00 m from the center of the turntable, we have;
[tex]\displaystyle F_f = \mu_s \cdot m \cdot g = \mathbf{ m \cdot r_1 \cdot \omega_1^2}[/tex]
[tex]\displaystyle\mu_s \cdot g = r_1 \cdot \omega_1^2[/tex]
[tex]\displaystyle\mu_s = \frac{r_1 \cdot \omega_1^2}{g} = \mathbf{\frac{r_1 \cdot \left(\displaystyle \frac{J_0 \cdot \omega_0}{J_1}\right)^2}{g}}[/tex]
Which gives;
[tex]\displaystyle\mu_s =\frac{3 \times \left(\displaystyle \frac{3,828 \times \frac{2 \cdot \pi}{8} }{1,857}\right)^2}{9.81} \approx \mathbf{0.802}[/tex]
The coefficient of static friction between the bottom of the feet and the surface of the turntable, at 3.00 m from the center, [tex]\mu_s[/tex] ≈ 0.802.
Learn more about the conservation of angular momentum here:
https://brainly.com/question/11259397
