International Physics Olympiad

IPhO 1968

Budapest, Hungary · 3 theory problems with complete solutions

  1. Problem 1: Solid cylinder and block joined by a cord on an inclined plane

    On an inclined plane of \(30^\circ\) a block, mass \(m_2 = 4\) kg, is joined by a light cord to a solid cylinder, mass \(m_1 = 8\) kg, radius \(r = 5\) cm (Fig. 1). Find the acceleration if the bodies are released. The coefficient of friction between the block and the inclined plane \(\mu = 0.2\). Friction at the bearing and rolling friction are negligible.

    Figure 1

    Figure 1

    Official English text of the problem.

  2. Problem 2: Mixing two quantities of toluene at different temperatures

    There are \(300\ \mathrm{cm}^3\) toluene of \(0^\circ\mathrm{C}\) temperature in a glass and \(110\ \mathrm{cm}^3\) toluene of \(100^\circ\mathrm{C}\) temperature in another glass. (The sum of the volumes is \(410\ \mathrm{cm}^3\).) Find the final volume after the two liquids are mixed. The coefficient of volume expansion of toluene \(\beta=0.001({}^\circ\mathrm{C})^{-1}\). Neglect the loss of heat.

    Official English text of the problem.

  3. Problem 3: Parallel rays refracted by a glass semi-cylinder

    Parallel light rays are falling on the plane surface of a semi-cylinder made of glass, at an angle of \(45^\circ\), in such a plane which is perpendicular to the axis of the semi-cylinder (Fig. 4). (Index of refraction is \(\sqrt{2}\).) Where are the rays emerging out of the cylindrical surface?

    Figure 1

    Figure 4

    Official English text of the problem.