Math Problem Statement

A mountain climber in the process of crossing between two cliffs by a rope, pauses to rest. The cliff to the left has a 65.0 degree angle and the cliff to the right has an 80.0 degree angle. She weighs 550 N. She is closer to the left cliff than to the right cliff, with the result that the tensions in the left and right sides of the rope are not the same. Find the tensions in the rope to the left and to the right of the mountain climber.

Solution

To find the tensions in the rope on both sides of the mountain climber, we can use the equilibrium conditions. Since the climber is at rest, the sum of forces in both the vertical and horizontal directions must equal zero.

Let:

  • TLT_L be the tension in the rope on the left side.
  • TRT_R be the tension in the rope on the right side.
  • θL=65\theta_L = 65^\circ is the angle of the left side of the rope with the horizontal.
  • θR=80\theta_R = 80^\circ is the angle of the right side of the rope with the horizontal.
  • W=550NW = 550 \, \text{N} is the weight of the mountain climber.

Step 1: Vertical force balance

In the vertical direction, the sum of the vertical components of the tensions must balance the weight of the climber:

TLsin(θL)+TRsin(θR)=WT_L \sin(\theta_L) + T_R \sin(\theta_R) = W

Substituting the known values:

TLsin(65)+TRsin(80)=550T_L \sin(65^\circ) + T_R \sin(80^\circ) = 550

Step 2: Horizontal force balance

In the horizontal direction, the horizontal components of the tensions must cancel each other out:

TLcos(θL)=TRcos(θR)T_L \cos(\theta_L) = T_R \cos(\theta_R)

Substituting the known angles:

TLcos(65)=TRcos(80)T_L \cos(65^\circ) = T_R \cos(80^\circ)

Step 3: Solving the system of equations

Now we solve these two equations simultaneously:

  1. TLsin(65)+TRsin(80)=550T_L \sin(65^\circ) + T_R \sin(80^\circ) = 550
  2. TLcos(65)=TRcos(80)T_L \cos(65^\circ) = T_R \cos(80^\circ)

From equation 2, solve for TLT_L:

TL=TRcos(80)cos(65)T_L = T_R \frac{\cos(80^\circ)}{\cos(65^\circ)}

Substitute this expression for TLT_L into equation 1:

TRcos(80)cos(65)sin(65)+TRsin(80)=550T_R \frac{\cos(80^\circ)}{\cos(65^\circ)} \sin(65^\circ) + T_R \sin(80^\circ) = 550

Factor out TRT_R:

TR(cos(80)sin(65)cos(65)+sin(80))=550T_R \left( \frac{\cos(80^\circ) \sin(65^\circ)}{\cos(65^\circ)} + \sin(80^\circ) \right) = 550

Now compute the trigonometric values:

  • sin(65)0.9063\sin(65^\circ) \approx 0.9063
  • cos(65)0.4226\cos(65^\circ) \approx 0.4226
  • sin(80)0.9848\sin(80^\circ) \approx 0.9848
  • cos(80)0.1736\cos(80^\circ) \approx 0.1736

Substitute these into the equation:

TR(0.1736×0.90630.4226+0.9848)=550T_R \left( \frac{0.1736 \times 0.9063}{0.4226} + 0.9848 \right) = 550

Simplify:

TR(0.15730.4226+0.9848)=550T_R \left( \frac{0.1573}{0.4226} + 0.9848 \right) = 550 TR(0.3722+0.9848)=550T_R \left( 0.3722 + 0.9848 \right) = 550 TR×1.357=550T_R \times 1.357 = 550

Solve for TRT_R:

TR=5501.357405.5NT_R = \frac{550}{1.357} \approx 405.5 \, \text{N}

Step 4: Find TLT_L

Now that we know TRT_R, substitute it back into the expression for TLT_L:

TL=405.5×cos(80)cos(65)=405.5×0.17360.4226T_L = 405.5 \times \frac{\cos(80^\circ)}{\cos(65^\circ)} = 405.5 \times \frac{0.1736}{0.4226} TL405.5×0.4108166.5NT_L \approx 405.5 \times 0.4108 \approx 166.5 \, \text{N}

Final Answer:

  • The tension in the rope to the left of the climber is approximately TL166.5NT_L \approx 166.5 \, \text{N}.
  • The tension in the rope to the right of the climber is approximately TR405.5NT_R \approx 405.5 \, \text{N}.

Do you want more details, or have any questions?

Here are some related questions to explore:

  1. How does changing the angle on either side affect the tensions in the rope?
  2. What happens to the tension if the climber’s weight increases?
  3. What if the climber moves to the exact middle between the cliffs—how would that change the tensions?
  4. How would the tensions change if the angle on the right side was less than on the left?
  5. How would the solution differ if the angles were exactly the same?

Tip: In equilibrium problems, always remember that the net force in both horizontal and vertical directions must be zero!

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Math Problem Analysis

Mathematical Concepts

Statics
Equilibrium
Trigonometry

Formulas

Vertical force balance: TL * sin(θL) + TR * sin(θR) = W
Horizontal force balance: TL * cos(θL) = TR * cos(θR)

Theorems

Equilibrium conditions in mechanics

Suitable Grade Level

Grades 11-12