Physical mechanics, mechanics, optics! Mechanics Physics

Ah, it depends on the individual, when I was in school, mechanics was very good, optics was good, electricity was almost, I don't know if you are in high school, or go to college, or junior high school,,, we didn't have optics in junior high school, and now ,,, who knows.

High school,I guess you are high school,,I graduated not long ago,,Mechanics is the deepest,But mechanics is the basic thing,Master the law,Learning is still simple,,Optics I feel is a very complex thing,But high school does not involve much,Just simple long wave and short wave,Reflection and refraction,At most, what is the Polly two image line,I don't know if I made a mistake,,, I was embarrassed to forget the light,,, although I don't involve much, but I can't bear it, disgusting, it's either simple, or it won't ,,, In addition, it is also electricity with the magnetism association.,Just mechanics.,Magnetism.,There's this kind of topic together with the electricity association.,Generally the last one.,It's okay.。

Comparatively speaking, optics is simpler, physical electricity is the most difficult, and mechanics is secondary.

Mechanics, Electricity, These are very wide, mechanics has theoretical mechanics, electrodynamics, fluid mechanics, analytical mechanics, etc., and so on, and there are many different types of electricity, and mechanics is the most difficult to learn.

It depends on how much you want to learn, if you learn deeply, there are difficult places, do you want to choose a major? It depends on your own interests, there is no such thing as simplicity in physics.

Let's answer the second question first. If a person stands on the ground.

Is there an action force and a reaction force? Yes. The action and reaction forces are that a force is applied on b, and b exerts a force of the same magnitude but in the opposite direction on a.

weight) The weight of man w is the gravitational pull of the earth [[acting on man]]. The man also exerts a force w of the same magnitude but in the opposite direction on the earth'。w and w'A pair of action and reaction forces is formed.

Since the earth [[exerts a normal reaction] r on him, that man also exerts a force r of the same magnitude on the earth, but in the opposite direction'。r and r'It also forms a pair of action and reaction forces. - Question 1.

Not necessarily. See from the GE example above.

Normal reaction and buried weight are both applied to the same object [[person]] degree.

So they are not a pair of action and reaction forces.

No. Because according to Newton's third law, the action and reaction forces are the forces exerted by object A on object B, and the forces exerted by object B on object A, which are usually large and small but in opposite directions. But normal reaction is the force exerted on the surface of the object, while weight is the force exerted by the earth on the object, and the two forces are not just about the two objects.

Example: If the object is placed on an inclined board, normal reaction and weight are not in the opposite direction. Examples of action and reaction forces:

When skiing, use two sticks to push yourself forward. Force: The force exerted by the rod on the snow, the reaction force:

Snow is applied to the force of the stick (so forward).

Reference: me

The pressure is f, which means that the child's gravity is mg=f (because this is at rest) and the swing board is off the beam of the hanging swing Description r=

So: f direction = mv r

16f because n-mg=f.

So: n = f to +mg

Hope it helps the landlord!

f=mg

f1-f=mv²/r

f1=f+16m/

The amount of pressure on the swing board when the child passes through the lowest point is 3 2 f

Directly seen as a circular motion understood?

The weight of the child plus centrifugal force is the pressure on the Qianqiu board.

The simplest method is to calculate the average velocity of a certain movement equal to the instantaneous velocity at the intermediate moment of the movement in a linear motion with uniform speed.

Since the displacement in the first second is meters, the average velocity in this second v1=s t=2m 1s = 2m s, that is, the instantaneous velocity at the end of the second in the middle moment of this movement, is denoted as, and because the displacement in the fifth second and the sixth second is summed, the average velocity in the two seconds v2 = is the instantaneous velocity at the end of 5 seconds in the middle of the two seconds, denoted as v5=

The time taken from the beginning to the end of the second is the instantaneous velocity at the end of the second and the velocity at the end of 5 seconds is used as the final velocity.

If t= then the acceleration a=(

Q2: The displacement in the sixth second can be obtained by multiplying the average velocity of the movement by the time. The average suspect velocity in the sixth second is equal to the instantaneous velocity at the end of the middle moment of the movement, which is obtained by the velocity formula.

The displacement in the sixth second is the average velocity of this movement 6m s multiplied by this time period of 1s, which is 6m

In kinematics, it is very simple to use the average velocity equal to the instantaneous velocity at the intermediate moment of the motion, because only the average velocity formula v=s t is used here, and this average velocity is converted into the instantaneous velocity at the intermediate moment. Finding acceleration avoids the squared arithmetic, simplifying the calculation.

The methods of the few downstairs, except for "My love can't be shared|.""Except for the classmates' mistakes, everything else is right.

1) Set a certain time to t and the speed to v0

s1=v0(t+1-t)+1 clear disturbance 2a((t+1) -t )=2v0+1 2a(2t+1)=2

v0+at+a/2=2...1)

S5+S6=V0(T+6-(T+4))+1 Erection 2A((T+6) Spinning Fiber Denier-(T+4) )

2v0+1/2a(2t+10)*2=

2v0+2at+10a=

v0+at+5a=

2)-(1)：9a/2=

a=2) v0+at+ v0+

s6=v0(t+6-(t+5))+1/2*v0+1/2*v0+

1。The local divination shed is known by the law of uniform variable speed motion, δx5 + δx6-δx1 = 10at square, so bring in data to get a = square.

2.Because the displacement of the object in two time periods is known, the velocity in the 6th second is v=x t=, and the time of the disadvantage is known, and the acceleration of the tung is known, so the displacement in 6 seconds is.

Method 1: s=vt+1 2*at 2

t=1 v+1 2*a=2

t=6 minus t=4 (6*v+1 2*a*36)-(4*v+1 2*a*16)=

The system of binary hall collapse equations can be solved a= v=

The displacement is 6 meters in six seconds.

Brother Fang and Law 2:

s5=s1+4at s6=s1+5at

s5+s6=2s1+9at= where s1=2 t=1 is solved to obtain a = six dust displacements in seconds s6 = 6

s=v*t+1/2a*t^2

2=v+1/2a --

s4=4*v+1/2*a*4*4=4v+8as6=6v-1/2*a*6*6=6v+18as6-s4= --

The magnitude of the acceleration of this particle is a = meter yards less than seconds squared.

v = the hail mode of the source field within the sixth second of the particle displacement, s=s6-s5s=6v+1 2*a*6*6-5v-1 2*a*5*5=6 (m).

Friction is a principle: f = n, and n is the supporting force.

Since there is no displacement of the object in the vertical direction of the inclined plane in this problem, the supporting force of the inclined plane to the object n=mgcos (the component of gravity in the direction of the vertical inclined plane).

So f= n= mgcos

Option C, because the density of the object is less than that of water according to the gravity and volume given in the question, the wooden block and the object are both floating on the water surface after separation, so the buoyancy is still equal to the gravitational force of the wooden block plus the object. According to the buoyancy calculation formula, the volume of the two in the water is equal to the body of the wooden block in the water at the beginning. Therefore choose C

C should be selected, the liquid level remains unchanged, and the density of the object is calculated first, (, that is, it is smaller than the density of water, then the object is also floating on the water.

c, buoyancy = water density volume gravitational acceleration.

Decline. There is p gs1d1=pg s2d2=m2g+m1g when the object is placed on the wooden block, and pgs1d1 when the object is not placed'=pgs2d2'=m2g

p water density, g gravitational acceleration, s1 container water area, s2 wood block bottom area, d1 height of water rising, d2 height of wood block sinking, m1 mass of the object, m2 wood fast mass) so d1 > d1', i.e. the water level of the container drops.

c.No change.

The mass of the wooden block and the object does not change, and the volume of the drained water does not change.

The knowledge points are blurred, and it is best not to do the questions, but to sort out the knowledge points, my freshman year, my experience is in the following knowing questions, and I haven't been yet, but I hope it will be useful to you.

The teacher said, you can't listen to it, try to see the knowledge points to be reviewed before the teacher class, just browse it, don't just listen during class, the teacher said the knowledge points, you use notes, even if there is a material, it is not so easy to sleep when writing, I am like this, hehe, and go out of class to breathe fresh air outside the classroom, and drink more water, and go to the toilet more.

Also, you have to correct your mentality, there are many ways out for people, the college entrance examination is just one of the best ways to go, you have to be frank, the college entrance examination is essentially just a test, see how much material you have, but people take it too seriously, and you will be anxious if you value it. Be calm, the third year of high school is still very good, so you can understand a lot.

If the review is efficient, the knowledge points are clearer, and the mentality is correct, will the song be played during the exam? Hehe.

What we have to keep is openness and seriousness about every knowledge point.

After class, read the book carefully, master the basic knowledge, and then do the appropriate amount of exercises.

Everything is in your mood! This is one of my principles ...... being a human beingHehe.

Isn't it just the college entrance examination, why are you panicking, we are all from ......In fact, physics is really simple, and it can be ......done in three months and so onAs for things like building self-confidence, it's actually pretty straightforward ......To put it bluntly, I think that self-confidence is something that someone can comparatively obtain! In fact, comparison should not exist, people's talents are not the same, so there is no point in comparison, as long as you are a little narcissistic, it can be regarded as a self-confidence ......

In the past, when I studied physics, I used the "continuous questioning method", that is, when you encounter a problem, you keep asking, why is it like this, not like that, it seems to be a very simple question, you can ask a lot of whys in a row, so that you can review many chapters. In fact, when you ask a lot of why, you will find that what you ask will eventually return to the concept in the book, and then you will truly appreciate the greatness of Newton and other scientists! Maybe that's when you'll fall in love with physics......

Hehe, it's a personal experience.

Good luck with your exams......

There is a cut-off force at Da, B, which is equal in magnitude and horizontal force, and the rope is the effect force as the motive force.

2mgtanb = mg*sina cosa = 2tanb = tana selection.

Although there is no line, in fact there is a cut-off force at A and B, which is equal in magnitude and horizontal force, and the rope acts as the motive force for the effect.

2mgtanb=mg*sina cosa=2tanb=tana, choose d

If an object is subjected to three forces that are not parallel but are in equilibrium, it can be seen that the three forces must have something in common, and then there is the geometric relationship.

Answer: I don't understand the above two statements: Are you a college student?