Math Problem Statement

The spring shown in (Figure 1) is compressed 48 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30∘ incline is 0.16 .

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Figure1 of 1 A 100 kilogram person is sitting on the top of a curved slope, 10 meters above its bottom. The person leans against a horizontal spring with a spring constant of 80000 newtons per meter. On the other side of the slope, a 30 degree incline extends upward. Part A Part complete What is the student's speed just after losing contact with the spring? Express your answer with the appropriate units. v

14 ms Previous Answers Correct Part B How far up the incline does the student go? Express your answer with the appropriate units. Activate to select the appropriates template from the following choices. Operate up and down arrow for selection and press enter to choose the input value typeActivate to select the appropriates symbol from the following choices. Operate up and down arrow for selection and press enter to choose the input value type

Δs

Solution

To solve part (B), we need to calculate how far up the incline the student travels. The energy considerations will guide us through this process.

Step 1: Energy conservation and work-energy principle

The initial energy of the system is the kinetic energy of the student just after losing contact with the spring. This energy is used to do two things:

  1. Work against gravity to lift the student up the incline.
  2. Work against friction.

The total initial energy is the student's kinetic energy: KE=12mv2KE = \frac{1}{2} m v^2 where:

  • m=100kgm = 100 \, \mathrm{kg}
  • v=14m/sv = 14 \, \mathrm{m/s}

The energy is expended in two ways:

  1. Gravitational potential energy gained: PE=mghPE = m g h where hh is the height the student reaches.

  2. Work done against friction: Wfriction=fkd=μkNdW_{\text{friction}} = f_k d = \mu_k N d where:

    • μk=0.16\mu_k = 0.16 (coefficient of kinetic friction),
    • N=mgcosθN = m g \cos \theta (normal force),
    • dd is the distance traveled along the incline.

Step 2: Relating height hh and incline distance dd

From trigonometry on the incline: h=dsinθh = d \sin \theta

Step 3: Combine equations

The total work-energy equation is: 12mv2=mgh+μkmgcosθd\frac{1}{2} m v^2 = m g h + \mu_k m g \cos \theta \, d Substitute h=dsinθh = d \sin \theta: 12mv2=mg(dsinθ)+μkmgcosθd\frac{1}{2} m v^2 = m g (d \sin \theta) + \mu_k m g \cos \theta \, d

Factor out mgdm g d: 12v2=gd(sinθ+μkcosθ)\frac{1}{2} v^2 = g d (\sin \theta + \mu_k \cos \theta)

Solve for dd: d=12v2g(sinθ+μkcosθ)d = \frac{\frac{1}{2} v^2}{g (\sin \theta + \mu_k \cos \theta)}

Step 4: Substitute the values

  • v=14m/sv = 14 \, \mathrm{m/s},
  • g=9.8m/s2g = 9.8 \, \mathrm{m/s^2},
  • θ=30\theta = 30^\circ,
  • μk=0.16\mu_k = 0.16.

Calculate sin30=0.5\sin 30^\circ = 0.5 and cos300.866\cos 30^\circ \approx 0.866: d=12(14)29.8(0.5+0.16×0.866)d = \frac{\frac{1}{2} (14)^2}{9.8 (0.5 + 0.16 \times 0.866)}

Step 5: Perform the calculation

  1. Calculate 12(14)2=98\frac{1}{2} (14)^2 = 98,
  2. Calculate 0.5+0.16×0.866=0.5+0.13856=0.638560.5 + 0.16 \times 0.866 = 0.5 + 0.13856 = 0.63856,
  3. Multiply 9.8×0.638566.2589.8 \times 0.63856 \approx 6.258,
  4. Divide 98/6.25815.65m98 / 6.258 \approx 15.65 \, \mathrm{m}.

Final Answer:

Δs=15.7m\Delta s = 15.7 \, \mathrm{m}

Let me know if you'd like further clarification or details! 😊


Related Questions:

  1. How does the spring constant affect the initial velocity?
  2. What happens if the incline angle is increased?
  3. How would doubling the mass impact the distance traveled up the incline?
  4. How does friction influence the energy lost in this scenario?
  5. Can this system be solved using force analysis instead of energy?

Tip: Always check your trigonometric values and units when solving incline problems!

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Math Problem Analysis

Mathematical Concepts

Energy conservation
Kinetic energy
Potential energy
Work-energy principle
Trigonometry in inclined planes

Formulas

Kinetic Energy: KE = (1/2)mv^2
Gravitational Potential Energy: PE = mgh
Work against friction: W_friction = μ_k N d
Trigonometric relation: h = d sin(θ)

Theorems

Work-Energy Theorem
Principle of Conservation of Energy

Suitable Grade Level

Grades 11-12