Find courseware on three common forces in mechanics

According to the nature, the force is divided into three types: gravity, elasticity and friction;

So the answer is: gravity, elasticity, friction

<> take the whole: fy=0 na+nd+ne-(4q+4q 2)=0 (1).

ma=0 m'+6nd+8ne-(2*4q+(4+4*2/3)(4q/2)）=0 (2)

Take cde: fy=0 nd+ne+nc-4q 2=0 (3) mc=0 2nd+4ne-(4*2 3)(4q 2)=0 (4) take bc: mb=0 -2nc-1*2q=0 (5) simultaneous solution on the 5 formula, can solve 5 support reaction forces, if the negative value is obtained, it shows that the actual direction of the force is opposite to the set.

As shown in the figure below, draw the force diagram, 1, the net force is 0, so there is:

Fa+FD+FE=20 4+10 4=120kN---12, with A as the rotating axis, the resultant moment is 0, so there is:

FD 6+FE 8=(20 4) 2+(10 4) 6---23, with E as the rotating shaft, the resultant moment is 0, so there is:

fd 4 + fa 8 = (20 4) 6 + (10 4) 2---3 together to solve the binding forces fa, fd, fe.

1.Since the forces are balanced as a whole, the resultant force in the horizontal direction is zero and the net force in the vertical direction is zero.

2.The horizontal direction A of the bearer to the left of the pressure belt collapse force qb then produces a stupid circle to the right binding force qb along the direction of the rod.

3.When the vertical direction a is subjected to a downward force p, a vertical upward binding force p <> is generated

The answer is b, because the force in the horizontal direction and the vertical direction does not change (unless the gravity of the trolley changes).

The friction on the ground when the trolley is stationary is 0 because he is in a horizontal position and has no tendency to move.

b Regardless of the stationary motion, the equilibrium force is applied in the vertical direction, the gravity is equal to the supporting force, the gravity is unchanged, and the pressure is unchanged.

There is no friction when at rest.

First of all, I will give you a diagram of the force analysis of an object

The object is subjected to friction, support, vertical gravity, and tensile force f along the inclined plane, then in such a force, the object starts to move from rest and moves 4m in 2s, then the object is moving with uniform acceleration.

After analyzing the motion state, we can calculate the acceleration along the inclined plane.

1) It can be calculated from the force analysis that the supporting force fn=mgcos37°=80n on the object, and the sliding friction on the motion of the object, f=fn* =mgcos37° =80, then the resultant external force f' of the object along the inclined plane direction is equal to the tensile force minus the component force and frictional force of gravity in the inclined plane direction, i.e.

f'=f-mgsin 37°-f

100-10*10*, from the question "the displacement of the object in 2 s is 4 m" and then according to the kinematic formula, there is 1 2at*t=s, substituting the number to calculate the acceleration a=2m s2, there is Newton's second law to know, f'=ma, substituting the acceleration value, and f can be calculated'=20n, which is calculated by substitution, = .

2) After removing the force, the resultant force of the object is down along the inclined plane, the acceleration is a=g*(sin 37°+cos 37° )=8 m s2, at the end of 2s, the velocity of the object is v=4m s, then after the force is removed, the object does a uniform deceleration motion and knows that the velocity is zero, and the time taken is t=v a=, so when the velocity of the object is reduced to 0, but because mgsin 37°-mgcos 37° is greater than 0, so in the absence of tensile force f, the object will slide along the inclined plane, At this point, the direction of the sliding friction experienced by the object is upward along the inclined face, then there is ma'=mgsin 37°-mgcos 37° to get the acceleration a when the object slides down'=4m s2 for 1 second, at which point the velocity of the object v'=4*1=4m s

3) The displacement is a vector quantity, and the distance is a scalar quantity, so here the motion of the object is divided into three stages, the first stage, 2s from the stationary starting motion, the displacement s1=4m, the second stage, after removing the force, the object does a uniform deceleration motion along the inclined surface, the displacement s2=1m, the third stage, the object does a uniform acceleration motion along the inclined surface, the displacement s3=-2m, so the displacement of the object in the S from rest starts s=s1+s2+s3=4+1-2m=3m.

The distance is l=4+1+2m=7m.

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1. The object is accelerated by stationary motion, and S1=4M, A1*T1 2=S, A1=2M S, V1=4M S, the object is subjected to an oblique upward pull force f along the inclined plane direction during the motion, the oblique downward gravity component mgsin = 60N, and the downward friction force of the inclined object mgcos. m*a1=f-mgsinθ-μmgcosθ

Obtain =2, remove the force f, and the force f, the force on the object along the inclined plane is f'=mgsin = 60n, friction f= mgcos = 20n, the inertial action of the object continues to travel upward to the velocity is zero. Let this time be t2 and the acceleration is'，a2=8m/s²，t2=，s2=1m。Therefore, the object moves downward from rest after continuing to move upward.

m*a3=f'-f,a3=4m s,1s after v=a3*1=4m s,s3=2m.

3. It refers to the displacement and distance of the object from the bottom to the description of problem (2). s=s1+s2-s3=3m, distance l=s1+s2+s3=7m

Hello classmates. Answer: Option A For example, the gravitational pull of the earth, the magnetic force and the force of attraction between the charged bodies.

b If the net force of the object is not zero, there must be acceleration, so the state of motion must change.

c False: The action and reaction forces exist and disappear at the same time.

D False There are three elements of force, and the same three elements are the same force. If it is transmitted, the force object and the force object will change, and the force will no longer be the previous force, so it cannot be transferred.

The answer is AA: For example, magnetism, gravitational force.

B: The force can only change the motion state of the object, C: When compressing the spring, the hand first gives a pressure to the spring to compress it, and then the spring compresses and then gives the hand an elastic force in turn!! This sentence is inherently wrong, and it is good to refer to the meaning of Newton's third law.

D: It's controversial now, but it's mostly wrong.

The answer is a, c, and d, the object does not need to be in contact with the earth when it is subjected to gravity, and the attraction and repulsion between the two charges do not require contact between the two magnetic poles; As long as the resultant external force is not zero, there will be acceleration, and the state of motion will change; Hanging an object with a rope that has a pulling force on the suspended object and this pulling force is equal to the gravitational force of the object.

In physics, a force can be represented in a diagram or a diagram of a force in order to visualize it

The diagram of the force is to accurately represent the three elements of a force, that is, the magnitude, direction and point of action of the force, so a scale should be attached to the diagram of the force, pointing out how many Newtons a certain length represents, using a proportional line segment to represent the magnitude of the force, using an arrow to indicate the direction of the force, and generally using the tail end of the arrow to represent the point of action of the force (there are also special).

So the answer is: scale; how many newtons; Diagram of force; Schematic diagram of force