Asian Physics Olympiad · Year 2015

Problems

Problem 1A simple pendulum of length $\ell$ carries a small mass $m$ . It is displaced to angle $\theta_0$ and released from rest. Neglect resistance. Find its speed and string tension at the lowest point. Assume the string, pulley, electrical source, or optical apparatus is ideal as stated, and neglect any effect not specified. State a clear sign convention, identify the physical Keep one model and sign convention throughout. Reuse each intermediate result with the same convention, then check that the answer has the required physical dimensions. (a) Set up the physical relation. (b) Find an intermediate quantity. (c) Obtain the answer and check its conditions and units.Solutions: 1
Problem 2One mole of a monatomic ideal gas is heated at constant pressure from $T_1$ to $T_2$ ( $T_2>T_1$ ). Given the gas constant $R$ , find the work done by the gas, the change in internal energy, and the heat absorbed. Assume the string, pulley, electrical source, or optical apparatus is ideal as stated, and neglect any effect not specified. State a clear sign convention, identify the physical Keep one model and sign convention throughout. Reuse each intermediate result with the same convention, then check that the answer has the required physical dimensions. (a) Set up the physical relation. (b) Find an intermediate quantity. (c) Obtain the answer and check its conditions and units.Solutions: 1
Problem 3Monochromatic light of frequency $f$ illuminates a metal with work function $\phi$ . Using Planck’s constant $h$ and the positive elementary charge $e$ , find the maximum photoelectron kinetic energy and stopping potential $V_s$ when $hf>\phi$ . Assume the string, pulley, electrical source, or optical apparatus is ideal as stated, and neglect any effect not specified. State a clear sign convention, identify the physical Keep one model and sign convention throughout. Reuse each intermediate result with the same convention, then check that the answer has the required physical dimensions. (a) Set up the physical relation. (b) Find an intermediate quantity. (c) Obtain the answer and check its conditions and units.Solutions: 1