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FrozenT [24]
3 years ago
13

One uniform ladder of mass 30 kg and 10 m long rests against a frictionless vertical wall and makes an angle of 60o with the flo

or. A man weighing 700 N could climb up to 7.0 m before slipping. What is the coefficient of static friction between the floor and the ladder
Physics
1 answer:
yuradex [85]3 years ago
3 0

Answer:

   μ = 0.37

Explanation:

For this exercise we must use the translational and rotational equilibrium equations.

We set our reference system at the highest point of the ladder where it touches the vertical wall. We assume that counterclockwise rotation is positive

let's write the rotational equilibrium

           W₁  x/2 + W₂ x₂ - fr y = 0

where W₁ is the weight of the mass ladder m₁ = 30kg, W₂ is the weight of the man 700 N, let's use trigonometry to find the distances

             cos 60 = x / L

where L is the length of the ladder

              x = L cos 60

            sin 60 = y / L

           y = L sin60

the horizontal distance of man is

            cos 60 = x2 / 7.0

            x2 = 7 cos 60

we substitute

         m₁ g L cos 60/2 + W₂ 7 cos 60 - fr L sin60 = 0

         fr = (m1 g L cos 60/2 + W2 7 cos 60) / L sin 60

let's calculate

         fr = (30 9.8 10 cos 60 2 + 700 7 cos 60) / (10 sin 60)

         fr = (735 + 2450) / 8.66

         fr = 367.78 N

the friction force has the expression

         fr = μ N

write the translational equilibrium equation

         N - W₁ -W₂ = 0

         N = m₁ g + W₂

         N = 30 9.8 + 700

         N = 994 N

we clear the friction force from the eucacion

        μ = fr / N

        μ = 367.78 / 994

        μ = 0.37

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Birds resting on high-voltage power lines are a common sight. the copper wire on which a bird stands is 1.28 cm in diameter and
nekit [7.7K]

Answer:

8\cdot 10^{-4} V

Explanation:

First of all, let's find the cross-sectional area of the copper wire. The radius of the wire half the diameter:

r=\frac{d}{2}=\frac{1.28 cm}{2}=0.64 cm=6.4\cdot 10^{-3} m

So the area is

A=\pi r^2 = \pi (6.4\cdot 10^{-3} m)^2=1.29\cdot 10^{-4} m^2

Now we can calculate the resistance of the piece of copper wire between the bird's feet, with the formula:

R=\rho \frac{L}{A}

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\rho=1.68\cdot 10^{-8} \Omega m is the resistivity of copper

L=4.12 cm=4.12 \cdot 10^{-2} m is the length of the piece of wire

A=1.29\cdot 10^{-4} m^2 is the cross-sectional area

Substituting, we find

R=(1.68\cdot 10^{-8} m^2)\frac{4.12\cdot 10^{-2} m}{1.29\cdot 10^{-4} m^2}=5.4\cdot 10^{-6} \Omega

And since we know the current in the wire, I=149 A, we can now find the potential difference across the body of the bird, by using Ohm's law:

V=IR=(149 A)(5.4\cdot 10^{-6} \Omega)=8\cdot 10^{-4} V

4 0
3 years ago
The magnetic flux that passes through one turn of a 18-turn coil of wire changes to 4.5 wb from 13.0 wb in a time of 0.072 s. th
zavuch27 [327]

We could answer the question through the help of Faraday's Law of Induction: 

Volts induced = - N•dΦ/dt

where N is the number of turns, and

Φ is the magnitude of the magnetic field. 


V = IR, or R = V / I 


V = -18 * [13Wb – 4.5Wb] / 0.072s 


V = -2125 volts the sign just specifies direction 


R = -2125V / 190 A 


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8 0
3 years ago
How do I convert 498.82 cg to mg
mezya [45]
<span><u><em>Answer:</em></u>
498.82 cg is equivalent to 4988.2 mg

<u><em>Explanation:</em></u>
cg stands form centigrams
mg stands for milligrams

From the standards of conversion, to convert from centi to milli, we multiply the amount ny 10

<u>This means that:</u>
1 centigram = 10 milligram

To convert 498.82 cg to mg, all we have to do is <u>cross multiplication</u> as follows:
1 cg ..................> 10 mg
498.82 cg .........> ?? mg

498.82 cg = </span>\frac{498.82*10}{1}<span> = 4988.2 mg

Hope this helps :)</span>
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the third answer is right.

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