Length is a concept that is defined as the measure of how far something extends from one end to the other.
Length can be measured in any of many ways, but most commonly it is measured in meters and centimeters.
Time is a very complicated concept when it comes to physics. It’s also one of the most difficult concepts in physics. This is because time is intimately linked with the four fundamental forces of nature: gravitation, electromagnetism, strong nuclear force, and weak nuclear force.
Time always flows forward. The flow of time does not depend on any external influence like radiation or gravity. All motion creates change which ultimately causes the flow of time to be different from point A to point B in its passage through the space-time continuum.
Mass is the property of an object that determines how difficult it is to accelerate and move.
In general, mass is a measure of the amount of matter in an object. It's one of two primary measures of inertia - the other being weight. Mass can be calculated from the density and volume of an object by dividing them into its component parts - atoms, molecules, and their constituents such as electrons and quarks.
The most common method for measuring mass is using a scale or balance.
Mass is measured in kilograms (kg) or pounds (lb). The SI unit for mass is the kilogram, which is the same as the international avoirdupois pound.
Mass may also be defined by its gravitational effects- it's what causes objects to have weight when they are pulled by gravity.