HC Verma Chapter 4 Problem 3 — Tension in a hanging string

Problem Statement

Solve the Newton’s Laws / mechanics problem: Solve the Newton’s Laws / mechanics problem: A 3 kg mass hangs from a string. Find the tension in the string. ($g = 10$ m/s²) Equilibrium: Tension = weight Step 1: $T = mg = 3 \times 10 = 30$ N. $$\boxed{T = 30\text{ N}}$$ Mass(es), forces, angles, and coefficients of friction as given $g = 9.8\,\te

Given Information

  • $\boxed{T = 30\text{ N}$

Physical Concepts & Formulas

Newton’s second law $\mathbf{F}_\text{net} = m\mathbf{a}$ is the fundamental relation between net force and acceleration. For systems of connected objects (Atwood machine, blocks on inclines), each body is treated separately with a free-body diagram, and the constraint equations (same rope length, etc.) link the accelerations.

  • $\mathbf{F}_{\text{net}} = m\mathbf{a}$ — Newton’s second law
  • Atwood: $a = (m_1-m_2)g/(m_1+m_2)$, $T = 2m_1m_2g/(m_1+m_2)$
  • $f_k = \mu_k N$ — kinetic friction

Step-by-Step Solution

Step 1 — Verify the result: Check units, limiting cases, and order of magnitude to confirm the answer is physically reasonable.

Step 2 — Verify the result: Check units, limiting cases, and order of magnitude to confirm the answer is physically reasonable.

Step 3 — Verify the result: Check units, limiting cases, and order of magnitude to confirm the answer is physically reasonable.

Worked Calculation

$$\boxed{T = 30\text{ N}}$$

Answer

$$\boxed{T = 30\text{ N}}$$

Physical Interpretation

The numerical answer is physically reasonable — matching expected orders of magnitude and dimensional analysis. The result confirms the theoretical prediction and provides quantitative insight into the system’s behaviour.


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