Physics Compulsory 1 Force Analysis How to Analyze 5

1 Select the research object. 2 Analyze gravity. 3. Look at which objects the object under study is in contact with, and whether they are stretched or squeezed between them, and analyze the elastic force.

4. Finally, analyze whether there is relative motion or relative motion trend between the selected object and the object extruded, and analyze the friction force. * It is not easy to see whether there is elastic force or static friction force, use the hypothetical method: assuming that there is such a force or no such force, whether the resultant force of other forces is zero or whether the direction of the resultant force of other forces is consistent with the direction of acceleration This point depends on whether the known conditions are a force balance problem or a force imbalance problem.

It all depends on understanding, first divided into horizontal and vertical directions, and then analyze the components of each force in different directions and the reaction force caused by it!

First list all the forces on the object, then select an orthogonal coordinate system, decompose the forces into various coordinate axes, and then list the equations of the forces according to the state of the object (acceleration or constant speed or stationary).

In fact, force analysis is the foundation of physical mechanics, and you can master it with more practice.

Gravity, support force, pressure, friction, air resistance, tension of the rope, elastic or tensile force due to spring deformation, etc., should not be difficult to analyze according to the state of the object. The parallelogram rule is used for the synthesis and decomposition of forces.

The resultant force of the force in the straight line in all directions of the object in the state of rest or in the state of uniform linear motion is zero (the acceleration is zero), and the net force on the straight line in the direction of the object's motion in the state of uniform linear motion is not zero (there is acceleration).

Uniform circular motion can analyze the cause of the centripetal force, which is named from the effect of the force, because it produces acceleration towards the center of the circle, so it is called the centripetal force. It is not some type of force that has a definite nature. On the contrary, a force of any nature can act as a centripetal force.

In fact, it can be a force of a certain nature, or a component of a force, or it can be the combined force of several forces of different properties pointing towards the center of the circle along the radius.

Do more, think more. Draw the map first, remember to draw with a ruler, so that the angle is obvious, 1 gravity 2 elastic force 3 friction 4 external force 5 others Remember to hair.

Do more and then understand and finally master.

If you don't have a picture, you must draw it yourself, just draw a sketch.

When re-analyzing the force, it is necessary to clarify the research object (if there are multiple objects, first study one and then another), and then it is necessary to determine the motion of the object, (according to the gravity, elasticity, friction and the smooth analysis of these 3 forces), and then when doing the problem, the correct force analysis can play a greater role.

Hope you succeed.

Since the rope does not care about gravity, its mass is also ignored, so that there is no difference between its acceleration and constant velocity. The constant force f is completely applied to the object through the rope, so that the object accelerates.

If the rope is to consider mass, then it and the object become a connector. In the integral analysis, the constant force f causes the rope and the object to produce a common acceleration. Then use the isolation method to analyze the force of the rope and the object, and it will be found that the force of the rope pulling the object is not equal to the constant force f.

Of course, the force on the rope is unbalanced.

So you're wrong not to think about quality at the beginning, but then to consider the impact of quality when you deal with it.

You should know how to isolate the law, but if you don't know, ask again. If you understand, please adopt it in time. ok

The rope will accelerate evenly.

And it accelerates the same as the acceleration of the object, but you should note that the mass of the rope is not taken into account here.

So the pulling force of the external force on the rope is equal to the pulling force of the rope on the object, in fact, here, the rope only plays a role in transmitting the external force.

If you consider the quality of the rope, then the magnitude of these two forces is not the same...

If there is a problem, you can continue to chase me.

Anyway, I liked physics and mechanics the most in high school, hehe.

You're right, the force on the rope is unbalanced during acceleration, but the title itself will say that the rope does not count gravity, f=ma, m=0, even if there is a then f=0 is not difficult to understand, in fact this is impossible.

Think of the rope and the object as a whole. The object and the rope are moved together by force.

It can also be understood in this way. The man gives the rope force f. The force that the block gives to the rope is only f1=umg. The forces are unbalanced. So make a uniform acceleration movement.

Please give the full question. The object has to be accelerated uniformly because the constant force is greater than the maximum static friction.

The rope pulls the wooden block to do a uniform motion, and the wooden block is subjected to tension, gravity and elastic force.

The mass of the rope is not counted, and you are choosing the rope as the research object, and you cannot perform dynamic analysis

The tension of the rope is equal to the friction of the ground, so it will balance and produce a uniform linear motion.

At this time, the rope should be analyzed as the object, the rope is subjected to a total of two forces (because gravity is ignored), one is the force f, the direction is forward, and the other is the pulling force of the object to the rope, the magnitude is equal to the sliding friction of the object, and the direction is backward, because f is greater than the sliding friction of the object, the resultant force is greater than zero, and the direction is forward. So the rope will do an even acceleration motion. That's it.

The uniform acceleration of the rope is the result of its constant force, so it is unbalanced.

The block of wood is subjected to a pulling force to the right and a frictional force to the left f pull minus f grinding which is equal to ma

I choose d but I'm a senior I don't remember the high school question clearly This question doesn't seem difficult to start with the original length of the spring above without force The object only receives the support force of the spring below Suppose the deformation of the spring below starts l1 , then.

mg=k2l

The mass of the object increases to 2 times, assuming that the object drops L2

Then 2mg=K2(L1+L2)+K1L2 is solved to obtain D

Option d When the object m is at rest: In order to counteract the gravitational force of the object, the spring below is compressed, and x1 is compressed. The spring above is not deformed by the question stem, and the force is 0.

Force balance on the object: mg=k2*x1, x1=mg k2

When the mass of the object is 2m: the object is analyzed, and the object is subjected to three forces: the upward pulling force of k1, the upward jacking force of k2, and the downward gravitational force, and the object drops by x.

Because the spring on it is not deformed, the object is deformed by x when it descends, and its pulling force on the object is k1*x. The object below has been compressed x1, and after the object drops x, it is compressed (x1+x), and its top force on the object is (x+x1)*k2.

There is 2mg = k1*x + k2*(x1+x). Bring in the result and calculate x.

Gravity first, then to see whether there is an electric field, the force of the magnetic field, and then the contact force, first analyze whether the force is balanced, unbalanced first look at the support force and then see the friction force. This is what I knew when I reviewed in my third year of high school.

The first field force (gravitational field, electric field, magnetic field) is seen to see whether it is balanced, and the unbalanced force is based on the contact force (support force, friction force), and the support force is first seen, and sometimes it can be balanced without friction.

Look at the problem first and determine the pair that should be analyzed by force. An object at rest on a plane, gravity, support force, if there is no sliding tendency, there is no frictional force. For an object sliding on a flat surface, gravity, support force, frictional force, frictional force and motion direction are opposite, if it is a smooth plane, friction needs to be considered.

An object at rest on an inclined plane, gravity, support force, frictional force along the inclined surface. The direction of friction of an object moving on an inclined plane depends on the motion.

In order, set a better memory by yourself, such as gravity, friction, and external force, mainly to classify the force, find a category and a category, and generally will not pull it down, followed by the decomposition of the force, to see which direction is easy to calculate, and the projection decomposition can be.

First, let's analyze the movement trend. Q to the right, P to the left, friction to stop the movement, to be contrary to the trend of movement.

Second, the analysis of p. The lower surface pressure of P is 2mg, and the friction of the ground to P is 2mgu to the right

The upper surface pressure of P is mg, the friction force of Q on P is the right MGU rope, and the tensile force on the rope is T=2MGU + MGU=3MGU Thirdly, the force on Q is analyzed. The lower surface pressure of q mg, the friction of p on q is to the left umg, so f=t+umg=3umg+umg=4umg

Lack of conditions! Do q and p move at a uniform speed? Is the ground smooth?

If it is a uniform motion, let the friction factor between p and ground be 1 and the friction factor between q and p be 2

Then for p, there is: 2 1mg + 2mg = t

For q there is: t + 2 mg = f

So f=2mg(1+2).