Time interval is the duration between two given times. Time is measured in different units, from seconds to millennia. Clocks and calendars are used for measuring time intervals
Percentage is a number or ratio represented as a fraction of 100. Percentage can be written as whole numbers, fractions, or decimals. Percentage is denoted by the symbol (%) or abbreviated as 'pct'
HCl is formed when hydrogen chloride gas mixes with water. It is a colourless gas with a pungent smell. Each molecule contains one-to-one ratio of hydrogen and chlorine. Commercial grades are slightly yellow due to impurities
Friction occurs when two surfaces come into contact and slide against each other. It acts opposite to motion direction and resists movement. Amount depends on surface roughness and pressing force
Buoyancy is the upward force exerted by fluids on submerged or floating objects. Archimedes' principle states that buoyant force equals fluid displaced by object. Objects float when their weight is balanced by fluid's upward force
Division is the process of dividing a large number into smaller equal parts. Division is the opposite of multiplication and involves repetitive subtraction. Division symbols are ÷ (obelus) and / (backslash). Division by zero is undefined and impossible