High School Physics. Newton s Laws, Newton s First Law in High School Physics

Solution: (Analysis: The object is placed on the belt, the speed is 0m s at the beginning, and the speed of the object must be slowly accelerated from 0m s to 3m s when the object runs with the belt, and the increase in this speed is accelerated by the friction force, that is, the acceleration a=ug m ss, after the object accelerates to 3m s, the speed remains the same and moves with the belt.

When the velocity of the object is 0m s to 3 m s: a=ug=2m ssThe distance of the accelerated motion of the object: s=1 2 *at 2 , t=v a=the time when the object moves at a uniform speed of 3m s t"=(x-s) v=So the time it takes for an object to get from A to B:

t=t"+ t=A: ......

This kind of problem is generally a period of acceleration and a period of constant speed.

a=μg=2

The distance taken to accelerate to 3m s is s=v 2 2a=time taken t=v a=time for the remaining section is t=s total -s v=seconds.

So the total time is seconds.

I haven't touched physics for 7 years, I only know the idea of solving the problem, I forgot the formula, and you have to set it yourself.

1* Friction.

Friction can be understood as power, that is, to find the acceleration a f=ma, you can find the answer by using the uniform acceleration formula, where s=6 v, the beginning of the = 3 formula, I forgot the specifics, or I will give you the answer, hehe, ask for it yourself

It used to be done, but now it won't!!

Newton's first law of motion, abbreviated as Newton's first law. It is also known as the law of inertia, the law of inertia. Common full statements:

Any object should remain in a uniform linear motion or at rest until an external force forces it to change its state of motion.

Newton's original formulation in the Principia Mathematica of Natural Philosophy was that any object should remain in a uniform linear motion or at rest until an external force forces it to change its state of motion. This expression has been cited in the high school physics textbooks of the People's Education Edition and the Cantonese Education Edition.

Newton's first law states: All objects always remain at rest or in a uniform linear motion under any circumstances when they are not acted upon by external forces.

Newton's second law states that the acceleration of an object is directly proportional to the resultant external force on the object, inversely proportional to the mass of the object, and the direction of acceleration is the same as the direction of the resultant external force. Formula: f = ma

Newton's third law states: The force of action and reaction between two objects, on the same straight line, is equal in magnitude and opposite in direction. Expression: f1 = f2, where f1 is the action force and f2 is the reaction force.

The law of gravitation is that any two objects in nature are attracted to each other, and the magnitude of the gravitational force is directly proportional to the product of the masses of the two objects, and inversely proportional to the square of the distance between the two objects. It is expressed by the formula as:

f=g*m1m2 (r*r) (g= can be read as f is equal to the square quotient of g multiplied by m1m2 divided by r.

f: gravitational force between two objects, g: gravitational constant, m1: mass of object 1, m2: mass of object 2, r: distance between two objects.

There is a stop in the oversale quarrel.

mgu=ma

where a=v t=1m (s 2).

Solution u=accelerate the key in the process of the draft, there is.

f*cos30°-un=ma‘

f*sin30°+n=mg

where a'=v' t'=2m (s 2), u=solution f=120 (1+10*root number 3).

The object at rest on the horizontal ground has a vertical mass of 2kg, and it begins to move under the impetus of a constant force f at an angle of 30 degrees obliquely upwards with the horizontal direction of Li Ming, and its velocity reaches 4m s at the end of 2s

Acceleration a1 = v t1 = 4 2 = 2m s 2m=fcos30°- Millixun mg + FSIN 30°) 2*2=F root number 3 2- (2*10+f 2)8 = F root number 3- (40+f).

f(root number 3-1) = 8+40

f=(8+40) root number 3-1) = (4+20 ) (root number 3+1).1)

At this point, F is withdrawn and stopped by the 4S object:

Deceleration a2 = v t2 = 4 4 = 1m s 2ma = mg

dDynamic friction coefficient: =a g=1 10=

Substituting = into (1) gets:

f = (4 + 20 * root number 3 + 1) = 6 (root number 3 + 1).

Newton's Three Laws.

Newton's three laws are important laws in mechanics, and they are the basis for the study of classical mechanics.

1 Newton's First Law.

Contents: Any object remains at rest or in a uniform linear motion until it is forced to change this state by the forces of other objects.

Explanation: Objects have a tendency to maintain rest and move in a uniform linear line, so the motion state of the object is determined by its motion speed, and its motion state will not change without external force. This property of an object is called inertia.

So Newton's first law is also known as the law of inertia.

Example) Let's say you are given an absolutely smooth bevel and a small ball slides down the top of the bevel and asks you what to do after that.

2 Newton's second law.

Contents: The object will produce acceleration under the action of the resultant external force, and the direction of acceleration is the same as the direction of the resultant external force, and the magnitude of the acceleration is proportional to the magnitude of the resultant external force and the inverse proportion of the inertial mass of the object.

The second law quantification is vector and is an instantaneous relation.

Example) In free fall, ignoring air resistance, gravity is the resultant external force on the object. g=ma (a is the acceleration and m is the mass).

Formula: f combined external force = ma

3 Newton's Third Law.

Contents: The action and reaction forces between two objects, on the same straight line, equal in magnitude and opposite in direction.

Note: To change the motion of an object, other objects must interact with it. The interaction between objects is manifested through force.

He also pointed out that the action of force is mutual, and there must be a reaction force. They act on the same straight line, equal in size and opposite in direction.

Also note:

1) There is no priority or priority between action and reaction forces. Creates and disappears at the same time.

2) This pair of forces acts on different objects and cannot be counteracted.

3) The action force and the reaction force must be forces of the same nature.

4) Nothing to do with the frame of reference.

Example) Slap the table, you apply a force to the table and the table also gives you a force, as soon as the hand is released, both disappear.

In general: the first law --- the law of inertia, the second law --- used to find acceleration, and the third law --- action and reaction forces. Your so-called formula is only found in the second law.

The water is overweight and the pellet is weightless, so the force of the water is pg'(a+g) p0g, a is the acceleration of the ball, the force of the ball is g'(1-a g), and Newton's second law can be obtained from a=(1-p p0)g, and g can be obtained by combining the above equation'-g'(1-p p0) 2, and because the glass of water weighs g, so g'+g-g'(1-p p0) 2,lz is also preparing for the first year of high school?

Let the friction force of the slope on the object be f, the inclination angle of the slope, the acceleration a1 when going up along the slope, the acceleration a2 when going down the slope, and the velocity vt when the object returns to the bottom slope

sinα=h/s=4/20=

According to the kinematic equation v0 2=2*a1*s, the substituting data is used to solve a1=, and the direction is downward along the inclined plane.

According to Newton's second law m*a1=m*gsin +f, then f=m*(a1-gsin )=10*(

According to Newton's second law m*a2=m*gsin -f, then a2=gsin -f m=10*

According to the kinematic equation vt 2=2*a2*s, then vt= (2*a2*s)= 2*

The correct conclusion is "(3 2)gsin".

1。Let the mass of the cat be m and the mass of the plank be 2m.

The cat's "position relative to the inclined plane does not change the slippery", and the force balances the sun.

The frictional force of the plank to the cat is equal to the "component of the cat's gravity along the inclined plane".

i.e.: f1=mgsin

2。The net force of the board is the sum of the "gravity of the board along the inclined plane" and the "friction force of the cat on the board".

f=f2+f1=(2m)sinα+mgsinα3。The acceleration of the plank sliding down the slope is:

a=(2msin +mgsin ) 2m=(3 2)gsin so there is no answer to this question.

Hello, draw the schematic diagram of the force as above.

When f is less than 2umg but greater than b, it will slide relative to the ground, so a is false, when f is equal to, a's acceleration is divided by 2m, that is, so b is false, when f is equal to 3umg, b's maximum rest friction on a is 2UMG, SO A'S ACCELERATION IS UMG DIVIDED BY 2M IS EQUAL TO ON THE OTHER HAND, A'S MAXIMUM REST FRICTION ON B IS ALSO 2UMG, SO B'S ACCELERATION IS DIVIDED BY M IS EQUAL TO IT IT CAN BE SEEN THAT WHEN F IS EQUAL TO 3UMG, THE ACCELERATION OF BOTH IS THE SAME, SO IT DOES NOT SLIDE RELATIVELY But option c says that f is greater than 3umg so the acceleration of a will be larger, but the acceleration of b is the same, so a slides relative to b, so c is correct.

No matter how large f is the acceleration of b is maximum, so d is correct.

The answer is as follows: (You didn't mention that A and B are close together.) First, use the integral method to analyze the force

1.The force pushes both to accelerate together, and the acceleration of AB is the same, so AA=AB=F (MA+MB).

With acceleration AB, the force it experiences can only be given by A, in the direction to the right, and the magnitude is ABMB=FMB (MA+MB).

According to Newton's third law, the force of b on a is to the left and is also fmb (ma+mb).

Is this the original question? Isn't that right?! Wrong.

Does AB exercise together?

If yes, a=f (ma+mb).

So the interaction force = mb*a = mb*f (mA+mb).

Using the kinetic energy theorem, the whole process has a ground force f and a gravitational force g

According to the kinetic energy theorem, both the initial kinetic energy and the final kinetic energy are 0,0=g

f=5g for C

Using the kinetic energy theorem: g(h+h)-fh=0, h=2m, h=, to obtain option c.