Object orparticleOfdisplacementIt is relative, which means that relative to a certain reference system, the displacement without a reference system is meaningless.If the displacement is not specified, it is generally based on the earthReference systemThat is, the displacement relative to the earth.
Motion is absolute, static is relative, and all objects in the universe are in motion.When we say that an object is stationary, we must mean that it is stationary relative to a reference object.
Object orparticleOfdisplacementIt is relative, which means that relative to a certain reference system, the displacement without a reference system is meaningless.If the displacement is not specified, it is generally based on the earthReference systemThat is, the displacement relative to the earth.
For example, if a person is walking on a moving car from the rear to the front and the car is running s, the car length L means the displacement of the person relative to the car is L, and the displacement relative to the earth is (s+L).A boat crossing a riverdisplacementThe displacement of the river relative to the river bank and the displacement of the boat relative to the river bank are both relative displacements.It should be noted that since displacements are vectors, their composition followsParallelogram rule。
Usually when we study the motion of an object, we do not emphasize which reference object the displacement (or speed, acceleration) of the object is relative to. That is because we have a convention: when we take the earth (or ground) asobject of referenceYou may not specify who the reference object is.However, when we use other objects as reference objects, we must clarify who is the reference object, or what the (relative) displacement or (relative) speed of an object is relative to whom.[1]
Related concepts
Announce
edit
Relative speed refers to the speed ofFrame of referenceThe speed measured for a reference object, such as air.Exercise is absolute,staticIt is relative. All objects in the universe are moving.When we say that an object is stationary, we must mean that it is stationary relative to a reference object.
Take boat crossing the river as an example:
The problem of small boat crossing the river is to discuss the relationship between the relative motion of "boat", "water" and "bank". The "ship to bank motion" is the combined motion of "ship to water motion" and "water to bank motion". The speed of ship to bank is usually called the ship's“Absolute speed”The speed of the ship relative to the water is called the "relative speed" of the ship, and the speed of the water relative to the shore is called“Implicate speed”。Therefore, the speed relationship of the above three relative movements can also be summarized as follows: the absolute speed is equal to the vector sum of the relative speed and the implicated speed.
Measurement method
Announce
edit
The sensors for measuring relative displacement are capacitive and eddy current, both of which are used to detect the gap change between the end face of the sensor and the measured object.Its biggest advantage is that it can detect not only dynamic displacement but also static displacement without contacting the measured object.[1]
