Math Problem Statement

Two identical strings making an angle of 𝜃 = 25.3° with respect to the vertical support a block of mass m = 13.7 kg (see the figure below). What is the tension in each of the strings? (Enter your answer in N.)

Solution

In this problem, we are asked to find the tension in each of two identical strings that support a block of mass m=13.7kgm = 13.7 \, \text{kg}. The strings make an angle θ=25.3\theta = 25.3^\circ with the vertical.

Step 1: Analyze the forces on the block

Since the block is in equilibrium (not moving), the forces acting on it must balance. The forces involved are:

  • The gravitational force (FgF_g) acting downward due to the block's weight, given by: Fg=mgF_g = mg where g=9.81m/s2g = 9.81 \, \text{m/s}^2 is the acceleration due to gravity and mm is the mass of the block.

  • The tension forces in the two strings, which we will call TT. Each string pulls upward at an angle θ=25.3\theta = 25.3^\circ from the vertical.

Step 2: Set up the force balance equations

Since the block is in equilibrium, the sum of the forces in both the vertical and horizontal directions must be zero.

Vertical direction:

In the vertical direction, the upward components of the tension forces must balance the downward gravitational force: 2Tcosθ=mg2T \cos \theta = mg where TT is the tension in each string, and the factor of 2 accounts for the two strings.

Horizontal direction:

In the horizontal direction, the leftward and rightward components of the tensions cancel each other, so we don't need to consider them for finding the tension.

Step 3: Solve for TT

Rearranging the equation for the vertical force balance to solve for TT: T=mg2cosθT = \frac{mg}{2 \cos \theta} Substituting the given values:

  • m=13.7kgm = 13.7 \, \text{kg}
  • g=9.81m/s2g = 9.81 \, \text{m/s}^2
  • θ=25.3\theta = 25.3^\circ

Now, calculate TT.The tension in each of the two strings is approximately 74.33N74.33 \, \text{N}.

Would you like further details on any of the steps, or do you have any other questions?

Here are 5 related questions to further explore this concept:

  1. How would the tension change if the angle θ\theta were increased?
  2. What would the tension be if the block's mass were doubled?
  3. How does the tension vary if only one string were used to support the block?
  4. What happens to the system if the angle θ\theta approaches 90°?
  5. How can we calculate the horizontal components of the tension forces?

Tip: When solving equilibrium problems, always check both the vertical and horizontal force balances.

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Math Problem Analysis

Mathematical Concepts

Statics
Trigonometry
Force Balance
Equilibrium

Formulas

Gravitational Force: F_g = mg
Vertical Force Balance: 2T cos(𝜃) = mg
Tension in each string: T = mg / (2 cos(𝜃))

Theorems

Newton's First Law of Motion (Equilibrium of Forces)

Suitable Grade Level

Grades 10-12 (High School Physics)