Particle is an idealized model. In the following examples, what can treat the research object as a particle is () A. Study the motion law of the earth around the sun B. Study the law of the alternation of day and night on the earth C. Study the time required for the train to run from Fuzhou to Shanghai D. Study the time required for a train to pass the Nanjing Yangtze River Bridge

Particle is an idealized model. In the following examples, what can treat the research object as a particle is () A. Study the motion law of the earth around the sun B. Study the law of the alternation of day and night on the earth C. Study the time required for the train to run from Fuzhou to Shanghai D. Study the time required for a train to pass the Nanjing Yangtze River Bridge

A. Study the motion law of the earth around the sun. The size of the earth can be ignored, so a is correct;
B. Studying the law of the earth's alternation of day and night, the earth can not be regarded as a point, the point has no size, and is simplified as a particle, so B is wrong;
C. When studying the time required for the train to run from Fuzhou to Shanghai, the length of the train is very small compared with the displacement, so the size of the train can be ignored and regarded as a particle, so C is correct;
D. Study the time required for a train to pass through Nanjing Yangtze River Bridge. The length of the train can not be ignored, so it can not be simplified as a particle, so D is wrong;
Therefore, AC

Deformation formula of uniform acceleration linear motion in senior one physics? Like the midpoint of displacement, the midpoint of time, and the initial velocity is not zero. After moving for a period of time and decelerating, there is also the maximum distance before the two objects meet in the pursuit problem

V=at
S=1/2at2
V=√2as
A=(vt-v0)/t
vt=v0+at
s= v0t+1/2at2
vt2-v02=2as

There are many formulas for uniformly accelerated linear motion in senior one physics. Who can tell me which formula should be used under what circumstances? V=at S=1/2at2 V=√2as A=(vt-v0)/t vt=v0+at s= v0t+1/2at2 vt2-v02=2as

The first three mentioned by the landlord are basically the same as the last three, except whether the initial speed is 0. They are basically the same. Pay attention to whether there are words with an initial speed of 0: "start at rest" and "stop after deceleration"... In fact, there are many. Usually pay more attention. The fourth is to move at a constant speed. Know the initial and final speed and time to calculate the acceleration. Pay attention to the initial and final speed, which is basically the definition of acceleration
Let's talk about the last three. In fact, there is no universal law. They are all limited to a certain scope of adaptation. Take the last three, the fifth and sixth. Their common feature is that they all have time T. If you require displacement and have time, of course, choose the sixth. If you don't have time, the last one!
The unknown quantity of each formula may be required! Just how many points are used to find the fifth and sixth of T. of course, the sixth pays attention to the fibrous root. The last two are very applicable to find the displacement. There are few problems using these three to find the acceleration
Basically, after doing the question, observe the question to see what it is and pay attention to individual words!
Add: all formulas mentioned by the landlord are only suitable for uniform speed linear motion

Simple formula derivation of linear motion with uniform speed change It is proved that the difference of displacement in any two consecutive equal time intervals (T) is a constant, that is: Δ x=xⅡ-xⅠ=xⅢ-xⅡ=…=xN-xN-1=aT^2

You draw a V-T (image of speed and time). Because it moves in a straight line with uniform speed change, the image should be a straight line. The area enclosed by the image and the x-axis in a certain period of time is the displacement in this period of time. If you subtract the area in adjacent equal periods of time, you will find that it is equal

Inference of six proportional relations of uniformly accelerated linear motion with zero initial velocity

(1) The ratio of instantaneous velocity at the end of 1s, 2S, 3S and... Ns is 1:2:3:...: n
v(n)=ant
v(n-1)=a(n-1)t
v(n-1):v(n)=(n-1):n (n>=2)
So: V (1): V (2): V (3). = 1:2:3
(2) For an object moving in a uniformly accelerated straight line with an initial velocity of zero, the displacement ratio at the end of 1s, 2S, 3S and... Ns is 1:4:9:
s(n)=1/2a(nt)^2
s(n-1)=1/2a((n-1)t)^2
s(n-1):s(n)= (n-1)^2:n^2
So: s (1): s (2): s (3). = 1 ^ 2:2 ^ 2:3 ^ 2
(3) The displacement ratio of an object moving in a uniformly accelerated straight line with an initial velocity of zero within 1s, 2S, 3S and... Ns is 1:3:5:... (2n-1)
s(n+1)=1/2a((n+1)t)^2
s(n)=1/2a(nt)^2
s(n-1)=1/2a((n-1)t)^2
s(n+1)-s(n)=1/2a((n+1)t)^2-1/2a(nt)^2
s(n)-s(n-1)=1/2a(nt)^2-1/2a((n-1)t)^2
s(n+1)-s(n):s(n)-s(n-1)=(n+1)^2-(n)^2:(n)^2-(n-1)^2
So it's: 1:2:3
(4) The ratio of the time it takes for an object moving in a straight line with uniform acceleration with an initial velocity of zero to pass through continuous equal displacement from rest is
In the same way, it is important to understand what it means

How to deduce the displacement formula of linear motion with uniform speed change?

S = V average * t
=[(vo+vt)/2]*t
=[(vo+vo+at)/2]*t
=[(2vo+at)/2]*t
=vot+1/2at^2