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Sagot :
kinematics were used able to find the answers
a) the horse must be at x = 9.39 m when the cowboy lets go
b) the correct answer about the padding is:
The cowboy would avoid injury if the director adds at least 42.7 cm of padding to the saddle., The exact value is y = 32.7 cm
given parameters
a) the horse's speed [tex]v_{c}[/tex] = 11.0 m / s
cowboy's initial height y₀ = 3.57 m
b) padding thickness
distance compressing the meat y = 3 cm (1 m / 100cm) = 0.03 m
to find
a ) the horizontal distance to the horse
b) need for padding
After reading this extensive problem we are going to solve it in parts
a) Let's use the laws of kinematics to find the time it takes the cowboy to reach the horse saddle, since his fall from rest begins, his initial velocity is zero
y = y₀ + v₀ t - ½ g t²
where y₀ is the initial height, and the height when it reaches the saddle (y = 0), v₀ the initial velocity, g the acceleration of gravity (g = 9.80 m / s²), t the time
0 = y₀ + 0 - ½ g t²
t = [tex]\sqrt{\frac{2y_o}{g} }[/tex]
t = [tex]\sqrt{\frac{2 \ 3.57}{9.8} }[/tex]
t = 0.854 s
this is the same time the horse must move, let's use the uniform motion ratios
[tex]v_c[/tex] = x / t
x = [tex]v_c[/tex] t
x = 11 0.854
x = 9.39 m
Therefore, using the concepts of kinematics, we find the distance that the horse must be for the cowboy to let go is x = 9.39 m
b) For this part we look in tables how much weight the bones of the spine resist and it is a value between 600 kg to 800 kg, therefore the weight that the spine resists
W = m g
W₁ = 600 9.8 = 5880 N
W₂ = 800 9.8 = 7840 N
To answer this part we use Newton's second law to find the maximum strength that the cowboy's column can resist, which is the maximum force (W2)
F = m a
a = 7840 / m
Let's start using kinematics to find the cowboy speed when he reaches the saddle.
v₁ = v₀ - g t
where v₁ is the velocity at the end of the interval, v₀ the initial velocity (v₀=0), g the acceleration of gravity and t the time
v₁ = 0 - g t
v₁ = - 9.8 0.854
v₁ = - 8.369 m / s
the negative sign indicates that the speed is down
now let's look for braking acceleration
v² = v₁² - 2 a y
when the cowboy stops his velocity is zero (v = 0)
0 = v₁² - 2 a y
y = [tex]\frac{v_1^2}{2a }[/tex]
y = [tex]\frac{8.369^2 \ m}{2 \ 7840}[/tex]
y = 0.00447 m
In order to complete the calculation, the cowboy mass is needed, suppose it is an average person
m = 80 kg
y = 0.00447 80
y = 0.357 m
y = 35.7 cm
This is the distance that the system must be compressed so that the force on the column does not exceed its breaking point. The thickness of the system is composed of the compression of the cowboy's meat plus the padding of the saddle
y = 3 + [tex]e_{chair}[/tex]r
[tex]e_{chair}[/tex] = 35.7 - 3
[tex]e_{chair}[/tex] = 32.7 cm
Therefore, withthe Newton's second law and kinematics, finding it the correct answer is
- The cowboy would avoid injury if the director adds at least 42.7 cm of padding to the saddle.
learn more about Newton's second law and kinematics here : brainly.com/question/19315467
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