Kinematics
2015-03-05 08:19:49 1 举报AI智能生成
Kinematics是物理学的一个分支，专注于研究物体的运动。它探讨了速度、加速度和位移等概念，以及它们之间的关系。通过分析物体的位置随时间的变化，可以推导出其运动轨迹和速度曲线。在二维空间中，可以使用向量来表示物体的位置和方向。而在三维空间中，则需要考虑更多的变量和方程。此外，Kinematics还研究了力的作用对物体运动的影响，包括牛顿定律和万有引力定律等。通过运用数学模型和实验数据，我们可以更好地理解物体的运动规律，为工程设计、交通运输等领域提供重要的参考依据。总之，Kinematics是一门富有挑战性和实用性的学科，对于深入探究自然界的运动现象具有重要意义。
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大纲/内容
newton's laws
First law
When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.
Second law
The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object: F = ma.
Third law
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
curvilinear motion
horizontal projectile motion
Y:1/2gt^2
X: vt
circular motion
centripetal force
F=mv^2/r=mw^2r
universal gravitation
The movement of planet
Kepler's first law
The orbit of every planet is an ellipse with the Sun at one of the two foci.
Kepler's second law
A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.
Kepler's third law
The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.
Law of universal gravitation
F=(G×M1×M2)/R²
astro navigation
first cosmic velocity 7.9 km/s
second cosmic velocity 11.2 km/s
third cosmic velocity 16.7 km/s
The description of movment
Element
Coordinate
One dimension
Two dimension
Reference system
Particle
A point with a mass
The description of speed
Velocity
Vector
average v = displacement traveled/ time elaspsed
instantaneous v = lim △t→0 △x/△t
Speed
Scalor
average speed = distance traveled/ time elaspsed
instantaneous speed = lim △t→0 △x/△t = instantaneous v
Time and Displacement
time: m/s
displacement: m
the difference between the final and initial position of a point
Rectilinear motion
constant motion
v is constant and a=0
motion with constant acceleration
a is constant and v is variable
Time and velocity
v = at
Time and displacement
x = vt + 1/2at^2
Displacement and velocity
2ax = vt^2 - v0^2
motion with variable acceleration
a and v is variable
movement of falling object
v=0 a=g
Interaction
Gravity
G=mg
Friction
Static
Kinetic
f=μN
Elasticity
Deformation
composition of forces
component of forces
law of conservation of mechanical energy
w=fs
p=w/t
elastic potential energy
1/2kx^2
gravitational potential energy
mgh
kinetic energy
1/2mv^2
theorem of kinetic energy
W=W1+W2+...+Wn
W=Ek2-Ek1
law of conservation of mechanical energy
△Ek=-△Ep
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