Floating bodies

Check purity of milk

Step 1: A lactometer is a device that measures the density of milk by floating in it. Step 2: Pure milk has a specific density, and when water is added, the density decreases. Step 3: The lactometer sinks to different levels based on milk's density - it sinks more in diluted milk. Step 4: By observing how deep the lactometer sinks, we can determine if water has been added to milk. Step 5: It doesn't measure temperature (thermometer does that), volume (measuring cups do that), or taste (our taste buds do that) - it specifically tests density to check purity.

76 cm of Hg

Step 1: Atmospheric pressure is the pressure exerted by the weight of air in Earth's atmosphere. Step 2: This pressure can support a mercury column of specific height in a barometer. Step 3: At sea level, standard atmospheric pressure supports exactly 76 cm (or 760 mm) of mercury column. Step 4: This measurement was first established by Torricelli using his mercury barometer experiment. Step 5: 100 cm, 50 cm, and 200 cm are incorrect values - 76 cm is the internationally accepted standard measurement for one atmosphere of pressure.

Buoyant force

Step 1: When an object is placed in a fluid (liquid or gas), the fluid exerts an upward force on it. Step 2: This upward force is called buoyant force or buoyancy, which opposes the weight of the object. Step 3: Buoyant force is caused by pressure difference at different depths in the fluid. Step 4: This force makes objects appear lighter when immersed in fluids and causes some objects to float. Step 5: Gravitational force pulls downward, magnetic force acts between magnets, and friction opposes motion - none of these describe the upward push from fluids.

Weight of displaced fluid

Step 1: Archimedes discovered that when an object is immersed in fluid, it experiences upward buoyant force. Step 2: This buoyant force is exactly equal to the weight of the fluid displaced by the immersed portion of object. Step 3: For example, if a stone displaces 50g of water, the buoyant force on stone is equal to weight of 50g of water. Step 4: This principle explains why ships float - they displace water weighing more than the ship itself. Step 5: The buoyant force doesn't equal object's weight (that would make everything float), volume (that's not a force), or density (that's not a forc