Physics Galaxy Discussion Questions Solutions May 2026

The Scenario: A ladder rests against a smooth wall and a rough floor. It slips. The standard textbook says the top loses contact with the wall before the bottom hits the ground. Discuss the violation of normal reaction.

Physics Galaxy Insight:

Do not just draw forces. Draw interactions. Ask: "What is touching the object? What fields are acting on it?"

Question

Solution

  • Combine: Add equations to eliminate T: m1 g − m2 g sin30° − μk m2 g cos30° = (m1 + m2) a.

  • Plug numbers (g = 9.8 m/s²): m1 g = 3·9.8 = 29.4 N. m2 g sin30° = 5·9.8·0.5 = 24.5 N. m2 g cos30° = 5·9.8·(√3/2) ≈ 5·9.8·0.8660 = 42.4 N. f_k = 0.2·42.4 = 8.48 N.

    Left-hand side = 29.4 − 24.5 − 8.48 = −3.58 N → negative indicates assumed direction wrong: system accelerates the other way (m2 down the incline, m1 up). Take magnitude for acceleration: a = 3.58 / (m1 + m2) = 3.58 / 8 ≈ 0.4475 m/s², directed so m2 moves down the incline.

  • Tension: Use m1 equation with sign consistent (m1 accelerating upward with magnitude a): T = m1 g − m1 a = 29.4 − 3·0.4475 ≈ 29.4 − 1.3425 = 28.06 N.

    • Question

    Solution

    0 - 0,00 €

    Service

    The Scenario: A ladder rests against a smooth wall and a rough floor. It slips. The standard textbook says the top loses contact with the wall before the bottom hits the ground. Discuss the violation of normal reaction.

    Physics Galaxy Insight:

    Do not just draw forces. Draw interactions. Ask: "What is touching the object? What fields are acting on it?" physics galaxy discussion questions solutions

    Question

    Solution

  • Combine: Add equations to eliminate T: m1 g − m2 g sin30° − μk m2 g cos30° = (m1 + m2) a.

  • Plug numbers (g = 9.8 m/s²): m1 g = 3·9.8 = 29.4 N. m2 g sin30° = 5·9.8·0.5 = 24.5 N. m2 g cos30° = 5·9.8·(√3/2) ≈ 5·9.8·0.8660 = 42.4 N. f_k = 0.2·42.4 = 8.48 N. The Scenario: A ladder rests against a smooth

    Left-hand side = 29.4 − 24.5 − 8.48 = −3.58 N → negative indicates assumed direction wrong: system accelerates the other way (m2 down the incline, m1 up). Take magnitude for acceleration: a = 3.58 / (m1 + m2) = 3.58 / 8 ≈ 0.4475 m/s², directed so m2 moves down the incline.

  • Tension: Use m1 equation with sign consistent (m1 accelerating upward with magnitude a): T = m1 g − m1 a = 29.4 − 3·0.4475 ≈ 29.4 − 1.3425 = 28.06 N. Solution

    • Question

    Solution