What Is Rectilinear Motion?
The path that a moving object passes is called the motion trajectory of the object. A motion trajectory is a linear motion, called a linear motion .
- Chinese name
- Linear motion
- Applied discipline
- physical
- Scope of application
- Physical kinematics
- When studying the motion of an object, a frame of reference must be selected
- Different reference systems for the same object may have different motion states
- The choice of frame of reference is arbitrary but should make objects and movements as simple as possible
- The ratio of time it takes for an object moving at a constant acceleration from stationary to pass through an equal displacement: 1: (2) -1: (3)-(2): ...: (n)-(n-1)
- Displacement ratio of an object moving at a constant acceleration from standstill through isochronous time: 1: 3: 5: ... 2n-1
- Vertical throw motion
- The path that a moving object passes is called the motion trajectory of the object. A motion trajectory is a linear motion, called a linear motion .
Definition of linear motion
- The position of the mass point is represented by the coordinate X as the distance from the origin. It is the basis for studying complex movements
- Uniform linear motion image
Linear motion classification
- rectilinear motion
- A trajectory is a linear motion of particles. Including two types of uniform linear motion and variable speed linear motion.
Linear motion displacement
- Represents the change in the position of the mass point. X is usually used to indicate displacement and is a vector. Formula : x = x2-x
- VT diagram of uniform linear motion
Linear motion
Linear motion concept
- Objects move on a straight line. If the displacements are equal in any equal time, this movement is called a uniform linear motion. When the resulting external force on a moving object is zero, the acceleration is zero, and the object moves in a straight line at a uniform speed.
Physical meaning of linear motion
- The relationship between reaction displacement and time.
- Variable-speed linear motion is a motion in which the speed changes but the direction does not change. When the resulting external force on a moving object is not zero, and its direction is on the same line as the direction of the object's speed, the object makes a linear motion with variable speed. When the external force is the same as the speed direction, the object performs a linear acceleration motion; when the external force is opposite to the speed direction, the object performs a linear motion deceleration. In the above case, if the magnitude and direction of the combined external force are not changed, the object performs a uniform acceleration linear motion or a uniform deceleration linear motion. For an object that moves at a constant speed and linear motion, the speed change amount is equal in any equal period; its initial speed and acceleration a (a is a positive value, which is a uniform acceleration motion; a negative value is a uniform deceleration motion), and the time elapsed is t The following three relationships exist between the distance s traveled and the final velocity . Free fall motion and vertical upward motion are two typical linear motions with uniform speed.
- Free fall. Only by gravity, an object that starts to fall is called free fall, and its movement is called free fall. This kind of motion is a uniform acceleration linear motion with zero initial velocity and acceleration g (gravitational acceleration, that is, 10m / s & sup2 ;, which is equivalent to g for junior high school to find the gravity of the object, but the units are different, please note.). The three formulas of free fall motion can be obtained by substituting the sum a in the above three relations with 0 and g.
- Vertical throw motion. Ascending and descending motions of objects thrown up vertically at an initial velocity. The ascending moving object is subject to gravity in the opposite direction to the speed, the speed gradually decreases, and the object makes a uniform deceleration movement. When the speed is reduced to zero, the object rises to the maximum height, and then falls back from this height to do free-fall motion. The problem of vertical throw motion can be calculated by the formula of uniformly variable linear motion with an initial velocity other than zero (where a = g).
Linear motion characteristics
- Objects move on a straight line and pass through the same displacement in equal time intervals. This kind of movement is called a uniform linear motion. For an object that moves in a straight line at a uniform speed, the ratio of displacement to time is a constant in different displacements or time periods, called the speed. The speed directly reflects the speed of the object's movement. In uniform speed linear motion, the average speed and instantaneous speed are the same, the magnitude and average speed of the average speed are also equal, and the displacement of uniform speed is proportional to time, which is expressed by the formula S = vt. The acceleration of an object moving at a constant speed is zero.
We call the linear motion with constant velocity the uniform rectilinear motion [1] (that is, uniform rectilinear motion), which means that the ratio of the distance and time that the object passes in any time period is a fixed value. Therefore, do not understand this formula from a mathematical point of view. The speed of an object's movement is directly proportional to the distance and inversely proportional to time. The object of making a straight-line motion at a constant speed is that the magnitude and direction of the instantaneous speed remain unchanged, and the acceleration is zero, which is an idealized movement.
Uniform linear motion is not common, we can think of some motions as uniform linear motion. Such as: a period of time after the skater stopped exerting force, the movement of customers standing on the escalator in the mall, and so on. We can use v = x / t to find their speed of movement, where x is displacement, v is velocity, it is a constant vector, and t is the time it takes for displacement x to occur. It can be seen from the formula that displacement is a time Function, displacement is proportional to time.
Note:
(1) The speed of an object that moves in a straight line at a constant speed is uniform. Therefore, if you know the speed of a certain moment (or a certain distance), you will know her speed at any time or at any point of movement.
(2) Unit of speed: In the international system of units, the unit of residence is m / s, and the commonly used units are km / h, m / min, etc.
(3) When an object is subjected to two forces, it can be said that the object is in equilibrium if it can remain stationary or move at a constant speed and straight line.
Linear Motion Reference System
- When describing the motion of an object, another object selected as the standard is called a reference frame.
- (Explanation):
Linear motion variable speed linear motion
Linear motion concept
- If a moving object travels unequal distances in the same amount of time (called "displacement" in high school), this movement is called variable speed movement.
- The variable speed motion of an object along a straight line is called variable speed linear motion.
Linear motion formula
- Uniformly variable linear motion
- Average speed V flat = s / t (definition formula)
- Useful Corollary Vt ^ 2-Vo ^ 2 = 2as
- Intermediate speed
- End speed
- Middle position speed Vs / 2 = [(Vo ^ 2 + Vt ^ 2) / 2] ^ (1/2)
- Displacement s = Vt t = Vot + (at ^ 2) / 2 = Vt / 2t
- Acceleration a = (Vt-Vo) / t {with Vo as the positive direction, a and Vo are in the same direction (acceleration) a> 0; reverse is a <0}
- Inference for experiment s = aT ^ 2 {s is the difference between displacements in consecutive adjacent equal time (T)}
Main physical quantities and units of linear motion
- Initial velocity (Vo): m / s; acceleration (a): m / s ^ 2; final velocity (Vt): m / s; time (t) seconds (s); displacement (s): meters (m); Distance: meters; speed unit conversion: 1m / s = 3.6km / h.
- Note: Free fall
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