The maximum speed of a vehicle with a rated power of 80kW can reach 20m / s when driving on a horizontal and straight road, and the mass of the vehicle is 2T. If the car starts to move in a straight line with constant resistance, the acceleration is 2 meters per second How long can the process of uniform acceleration be maintained? What is the real-time power of the last vehicle in 3.3 seconds? 4 how much work has been done by the automobile engine in the process of uniform acceleration? 3. It seems to be the fifth power of 48kW 4.2 * 10

The maximum speed of a vehicle with a rated power of 80kW can reach 20m / s when driving on a horizontal and straight road, and the mass of the vehicle is 2T. If the car starts to move in a straight line with constant resistance, the acceleration is 2 meters per second How long can the process of uniform acceleration be maintained? What is the real-time power of the last vehicle in 3.3 seconds? 4 how much work has been done by the automobile engine in the process of uniform acceleration? 3. It seems to be the fifth power of 48kW 4.2 * 10

1. When the speed of the car reaches the maximum, it will move in a straight line at a constant speed, and then p = f * VM, the resistance required is f = P / VM = 80 * 1000 / 20 = 4000 Newtons. 2. Suppose that the time that the car can maintain in the linear motion of uniform acceleration is t, the final speed of this stage is V1 (note not VM) f - F = ma

When the velocity of the bullet and the block is exactly equal, the displacement of the bullet is L1 and the displacement of the wood block is L2. If the friction force between the wood block and the block is f, then what work does the friction force do to the wood block? How much work does the friction force do to the bullet? What is the heat generated?

The friction force acting on the bullet is opposite to the direction of motion, that is, the direction of force is opposite to the direction of displacement, and the friction force of bullet does negative work. The friction force F1 of bullet is W1 = - F1 * L1 = - f * L1
The direction of friction on the wood block is the same as that of the movement, so the positive work is done. The work done by the friction force on the wood block W2 = f * L2
The work done by the friction force on the bullet reduces the kinetic energy of the bullet, and the work done by the friction force on the wood block increases the kinetic energy of the wood block. However, the decrease of the kinetic energy of the bullet is not equal to the increase of the kinetic energy of the wood block. However, the decrease of the kinetic energy of the bullet is equal to the sum of the kinetic energy increase of the wood block and the heat generated

If an object moving in a straight line has a velocity of 10m / s at a certain moment, then this object () A. The displacement must be 2m in 0.2S before this moment B. The displacement must be 10m within 1s after this moment C. The displacement may be 60m within 10s from this moment D. If starting from this moment, it will take 100s to continue to pass 1000m

A. In the first 0.2S of this moment, the object does not necessarily move in a uniform straight line, so the displacement is not necessarily equal to 2m
B. since this moment, the object does not necessarily move in a uniform straight line, so the displacement in 1s is not necessarily 10m
C. from this moment on, the displacement may be 60m in 10s
D. if you start to move in a straight line at a constant speed from this moment, x = VT, t = X
v＝1000
10 = 100 s. if a linear motion with constant speed is started from this moment, the time required for it to continue to pass the 1000m distance is not necessarily 100s
Therefore, C

Analysis of physical force in senior one Uniform balls a and B with radius R and weight of G are placed in a cylindrical container with a diameter of 3R. B is at the bottom and a is at the top. The two balls are in contact (the central line of the two balls and the line of action of the support force of the container bottom on the B ball are at an angle of 30 degrees)? Ask physics emperor to explain in detail!

With the integral method, AB is regarded as a whole. In force analysis, because the object does not move, the force is balanced on the whole, and the resultant force is zero in the horizontal direction and vertical direction respectively. For the whole body, there is upward support force and downward gravity stress in the vertical direction, so the supporting force is equal to the gravity of 2G, and the supporting force is the elastic force of the bottom of the container to B ball

The body is in a static state under the action of three common point forces. If one of the forces F1 is rotated clockwise by 90 ° to keep its size unchanged and the other two forces remain unchanged, then the resultant force on the body is () A. F1 B. 2F1 C. 2F1 D. Can't be sure

In force balance, the resultant force of any two forces is equivalent, reverse and collinear with the third force. Therefore, the resultant force of two forces except F1 is equal to F1, and the direction is opposite to F1. Therefore, it is equivalent to that an object is subjected to two forces with 90 ° to each other and equal to F1;
According to the rule of parallelogram, when two forces of equal size and 90 ° to each other are combined, the resultant force is on the angular bisector of the two components, so the resultant force on the object is
2F1；
Therefore, B

The balance of common forces 2. The dynamic friction coefficient between the object with weight g and the horizontal ground is μ, and the tension angle is α with the horizontal direction, which is inclined upward to the right. If the object moves along the horizontal direction in a uniform straight line under the action of tension, then the magnitude of the tension is f=_____ The direction of the resultant force of tension and friction is________ . 3. An object with a mass of 6kg is placed on a horizontal plane. In the same vertical plane, two forces, F1 (on the left) with the size of 20 pieces of 2n and the direction of 45 ° angle with the horizontal plane, and F2 with the size of 40n and the direction of 30 ° with the horizontal plane are used to lift it______ The role of their size is______ 、________ And________ . 4. An object placed on a horizontal ground receives a pull force F inclined to the upper right at an angle of α with the horizontal plane, which is used to move right along the horizontal plane at a constant speed. Then, the direction of the resultant force of the force F and the friction force F received by the object is______ . 5. Under the action of upward force F along the slope, the material block m on the inclined plane is in a static state, and the static friction force of the vamp acting on the five blocks is () A. The direction may be upward along the slope B. The direction may be downward along the slope C. The size may be zero D. The size may be equal to F Common point force has not understood, you great Xia many guidance

2. The dynamic friction coefficient between the object with weight g and the horizontal ground is μ, and the tension angle is α with the horizontal direction, which is inclined upward to the right. If the object moves along the horizontal direction in a uniform straight line under the action of tension, then the magnitude of the tension is f=__ Gu/(cosQ+sinQ*u)___ The direction of the resultant force of tension and friction is__ Vertical upward (balanced with gravity forces)__ .
3. An object with a mass of 6kg is placed on a horizontal plane. In the same vertical plane, two forces, F1 (on the left) with the size of 20 pieces of 2n and the direction of 45 ° angle with the horizontal plane, and F2 with the size of 40n and the direction of 30 ° with the horizontal plane are used to lift it__ Gravity, supporting force and static friction force_ The role of their size is_ 60N__ 、__ 20N_ And__ 20 (root 3-1) n__ .
4. An object placed on a horizontal ground receives a pull force F inclined to the upper right at an angle of α with the horizontal plane, which is used to move right along the horizontal plane at a constant speed. Then, the direction of the resultant force of the force F and the friction force F received by the object is vertical upward (balanced with the three forces of gravity)__ .
5. Under the action of the upward force F along the slope, the material block m on the inclined plane is in a static state, then the static friction force of the vamp acting on the five blocks is (a, B, c)
A. The direction may be upward along the slope
B. The direction may be downward along the slope
C. The size may be zero
D. The size may be equal to F

A body weighing 100N moves to the left on the horizontal plane, as shown in the figure. The dynamic friction coefficient between the object and the horizontal plane is 0.2. At the same time, when the object is subjected to a horizontal right force F = 20n, the resultant force on the object is () A. 0N B. 40n, horizontal left C. 40n, horizontal to the right D. 20n, horizontal to the right

When it moves to the left on the horizontal ground, the vertical direction is affected by gravity and support force, and the horizontal direction is subject to horizontal right tension and horizontal right friction force
The horizontal pulling force to the right is: F = 20n,
The friction force is: F = μ n = 20n,
So the resultant force is: F = 20 + 20 N = 40n, the direction is horizontal to the right,
Therefore, C

1. The ball is tied by light string and suspended on a static smooth slope. The ball mass is m = 0.5kg, the slope angle is 30 degrees, and the angle between suspension line and vertical direction is 30 degrees. The mass of smooth slope is 3kg. When placed on the rough horizontal plane, the whole device is in static state. G = 10m / S2 (1) (2) the magnitude and direction of the friction force between the ground and the inclined plane Why is there friction between the ground and the slope? Block a slides along the slope B at a constant speed, and B is still relative to the ground. In the question, the ground has no friction against the slope? Is it because the first question is a smooth slope? If there is friction force, is there no friction between the ground and the slope?

Integral method: consider the slope and the wood block as a whole. The whole is in balance in both cases. The rope gives the whole a horizontal component. Only the friction force of the ground is used to balance the force. Therefore, there must be friction force. In the second case, the whole body is not subjected to any external force along the ground direction, so

An object with a mass of 1kg, under the action of a horizontal constant force, starts to accelerate on a smooth horizontal plane from rest. Its displacement in T seconds is XM, then the size of F is () A. 2x T2 B. 2x 2t−1 C. 2x 2t+1 D. 2x t−1

According to the displacement formula: x = 1
2at2: a = 2x
t2．
According to Newton's second law, the horizontal constant force is: F = ma = 1 × 2x
t2＝2x
t2．
Therefore, a

19. When flying a kite, the plane of the kite is affected by the wind force F in the vertical direction. When the angle between the kite surface and the horizontal plane is satisfied, the maximum lift force is obtained by the kite. What is the maximum lift force?

We can know that the lift f '= f · cos θ, when θ = 0, cos θ = 1, then the kite surface is just horizontal, and the maximum lift force is f' = F