686

The image shows a page from a book, likely containing a series of physics or chemistry problems. Here’s a transcription of some of the problem numbers and key details mentioned:

• 686: The problem involves determining the force acting on a specific area of a piston exposed to external pressure.

• 687: This problem is about finding the temperature of a gas under certain conditions.

• 688: The problem mentions calculating the density of a liquid given in a vessel with specific parameters.

• 689: The task is to find the pressure exerted by a column of liquid with a given height and density.

• 690: This involves measuring how much water evaporates under certain conditions in a given timeframe.

Each problem likely requires applying principles of physics or chemistry related to pressure, density, temperature, and evaporation.