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Softa [21]
3 years ago
13

A girl is sledding down a slope that is inclined at 30º with respect to the horizontal. The wind is aiding the motion by providi

ng a steady force of 148 N that is parallel to the motion of the sled. The combined mass of the girl and the sled is 75.7 kg, and the coefficient of kinetic friction between the snow and the runners of the sled is 0.299. How much time is required for the sled to travel down a 124-m slope, starting from rest?

Physics
1 answer:
lapo4ka [179]3 years ago
7 0

Answer:

 travel time is 7.58 s

Explanation:

We must know the acceleration of the sled and the girl, for this we must use Newton's second law

      F = m a

Since this is a vector equation, let's separate it into its xy components, the best selection of the coordinate system is the X axis parallel to the plane and the Y axis perpendicular to it.

In the attached you can see a free body diagram of this situation, let's write Newton's equations on each axis

X axis

      Wx + F - fr = m a            (1)

Axis y

     N- Wy = 0

     N = Wy

Let's use trigonometry to find the weight components

    Wx = W sin θ

    Wy = W cos θ

In addition, the formula for friction force is

    fr = n N

Let's clear the acceleration of equation 1

   

    a = (W sin θ + F - m N) / m

    a = (mg sin θ + F - m mg cos θ) / m

    a = g (sin θ -m cos θ) + F / m

Let's replace and calculate

    a = 9.8 (sin 30 - 0.299 cos 30) + 148 / 75.7

    a = 2.36 + 1.96

    a = 4,317 m / s²

We already have the acceleration, the speed is zero to leave the rest (Vo = 0) and give the length that runs 124 m, let's use the kinematic equations

   x = v₀ t + ½ a t²

   x = ½ a t²

   t² = 2x / a

  t = √ 2x / a

 

Let's calculate

  t = √( 2 124 / 4,317) = √ 57.45

  t = 7.58 s

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shutvik [7]
Isothermal Work =  PVln(v₂/v₁)

PV = nRT =  2 mole * 8.314 J/ (k.mol) * 330 k = 5487.24 J

Isothermal Work =  PVln(v₂/v₁)            v₂ = ? v₁ = 19L, 

1.7 kJ = (5487.24)In(v₂/19)

1700 = (5487.24)In(v₂/19)

In(v₂/19) = (1700/5487.24) = 0.3098

In(v₂/19) = 0.3098

(v₂/19) = e^{0.3098}


v₂  =  19* e^{0.3098}

v₂ = 25.8999

v₂ ≈ 26 L        Option b.
6 0
3 years ago
A Styrofoam ball has just been shot straight up. Air resistance is not negligible (free body diagram)
timofeeve [1]

In a free body diagram for an object projected upwards;

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As the object accelerates upwards, its velocity decreases until the object reaches maximum height where its velocity becomes zero and as the object descends its velocity increases, which eventually becomes maximum before the object hits the ground.

To construct a free body diagram for this motion, we consider the following;

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<u>For instance:</u>

upward motion for velocity  ↑        downward motion for velocity  ↓

                                              ↑                                                            ↓

                                              ↑                                                            ↓

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Learn more here: brainly.com/question/13235430

5 0
3 years ago
Please help me , I also have to show work on paper
kramer

Answer:

Choose B

Explanation:

Hope Can I help you

7 0
3 years ago
Need amswer fast plz
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Answer:

I need this for may schooling

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Of the materials listed wood is the best insulator. It would be the least hot if exposed to similar temperatures.
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