How to find the resultant force? There is a question, please answer it, and feel free to help analyz

When the cart is pushed with 10N horizontal force F, the car moves at a constant speed, indicating that the resultant external force is zero at this time.

Friction force f = thrust f = 10n, the direction of friction is opposite to the direction of movement of the car, backward.

With f'=15nWhen pulling the car backwards, the car is still moving forward, so the direction of the frictional force is unchanged, backwards. And the magnitude of the frictional force remains the same.

So the net force at this point is f'+f=15n+10n=25n

Because the car moves at a constant speed, the force balance f=10n, the friction force is opposite to the relative direction of motion, and the deceleration motion car is still trying to run forward, so the resultant force at this time is f+f=20n

1.When a student is shopping in a supermarket, he pushes the shopping cart with a horizontal force of 10N to do a uniform linear motion on the horizontal ground, and the resistance of the trolley is 10N; Suddenly, he found that there was an old man in front of him, so he immediately used the horizontal force of 15N to pull the car backwards to slow down the car, and in the process of deceleration, the net force in the horizontal direction of the car was 5 N.

Explanation: When the shopping cart moves in a straight line at a uniform speed on the horizontal ground, the horizontal thrust given to the trolley by the classmate should be equal to the resistance of the trolley, so the resistance of the trolley is 10N. When the trolley is pulled backward with a horizontal force of 15N, the trolley is subjected to 10N resistance, and the backward horizontal force of 15N is opposite to the direction of 10N resistance, so the net force in the horizontal direction of the trolley is 5 N.

This 5n force causes the trolley to accelerate backwards.

The method of finding the resultant force is as follows:

1. Vector method. It is mostly used when the force is low.

Put the starting points of the force together and keep the direction of the force the same. This forms the two sides of the parallelogram. To complete this parallelogram, the diagonal between the original two forces is the resultant force of the two forces (the resultant force is calculated by solving the triangle), and the other diagonal is the difference between the two forces.

2. Orthogonal decomposition and synthesis method. It is used in the case of high force.

The force is changed to the x-axis and the force on the y-axis, and the algebraic addition and subtraction is performed. Finally, the resultant force of the force is obtained by the Pythagorean theorem.

If the effect of several forces acting on a particle together is the same as that of a force f, then this force f is called the resultent force of several forces.

Principle application:

The resultant force - the physics term force f direction is the direction of the synthesis of several forces.

Force is a vector quantity, and a repentant force refers to the sum of vectors of multiple forces acting on the same object together. The resultant force is a vector quantity, and the addition and subtraction of vectors satisfies the parallelogram rule and the triangle rule.

If the two forces are not collinear, the direction of the diagonal is the direction of the resultant force.

If the direction of the two forces is the same, then the resultant force is equal to the sum of the two forces and the direction does not change.

If the direction of the two forces is opposite, then the resultant force is equal to the difference between the two forces in the same direction as the direction of the larger force.

If the two forces are equilibrium forces, the resultant force is zero. ∑f=0。

If it can only be plotted, the unit length can be set by itself, as long as its proportion is the same as the Newton value, and the resultant force can only be found by the parallelogram method.

Make a parallelogram with two forces as the lengthening.

Then the resultant force is a diagonal with a fixed direction, and the value is its length.

Only when the angle between two forces is 90 degrees can the Pythagorean theorem be used.

Draw a diagram, move one of the lines to the end of the other line of force, connect end to end to form a triangle, and use the cosine theorem to find :

a2=b2+c2-2bccosa, so the magnitude of the two forces, and the angles, can be found using the cosine theorem.

The Pythagorean theorem is a special form of the cosine theorem.

The angle between the two forces is 120°, both forces are 100n, and they are translated to form an equilateral triangle, and the resultant force is equal to the component force.

Not vertical, you can use the following method:

Mathematics is available :

f^2=(f2+f1')^2+f1"^2=(f2+f1cosθ)^2+(f1sinθ)^2=f2^2+2f2f1cosθ+(f1cosθ)^2+(f1sinθ)^2=f2^2+2f2f1cosθ+(f1cosθ)^2+(f1sinθ)^2=f2^2+2f2f1cosθ+f1^2

So, the magnitude of the resultant force is :

f=√(f2^2+f1^2+2f2f1cosθ)

1.The concept of resultant force ......If the effect of a force is the same as that produced by the combined action of several forces, this force is called the resultant force of those forces, and those forces are called the component of this force. (The resultant force and the component force are equivalent substitution relations).

2.The resultant ...... of two forces of the same lineWhen f1 and f2 are in the same direction, the resultant force is the largest (the resultant force is in the same direction as f1 and f2, and the net force is f1+f2); When f1 and f2 are reversed, the net force is the smallest (the resultant force is in the same direction as the larger force in f1 and f2, and the net force is |f1-f2|）

3.The resultant ...... of two forces at angles to each otherForce is a vector quantity, and its composition follows the parallelogram rule (the range of values of the resultant force is |f1-f2|F-hop |f1+f2|）

4.The relationship between the magnitude of the resultant force and the magnitude of the angle between the two forces ......The magnitude of the resultant force f of the two common point forces f1 and f2 is related to their angles, and the larger the resultant force f, the smaller the resultant f.

The premise is that the force at the same point, with two forces as adjacent sides, makes a parallelogram, and the resultant force is a diagonal from the same point, understand? Multiple forces can be combined one by one.

It's called force-seeking synthesis.

The methods are: 1. Vector method. It is mostly used when the force is low.

Put the starting points of the force together, and keep the direction of the force the same. This forms a parallelogram.

on both sides. To complete the parallelogram, the diagonal between the original two forces is the resultant of the two forces (use Solve Triangle.

and the other diagonal is the difference between the forces of the two objects.

2. Orthogonal decomposition and synthesis method. It is used for the situation of the hood potato with a lot of force.

The force is changed to the x-axis and the force on the y-axis, and the algebraic addition and subtraction is performed. Finally, through the Pythagorean theorem.

The resultant force of the force is obtained.

There are many ways to achieve synergy, such as:

Method 1: Find the resultant force of two of the forces first, then find the resultant force of the first force and the third force, and then calculate it in turn to obtain the total resultant force.

But this method is more cumbersome.

Method 2: Use the polygon rule of force for synthesis.

All the forces are connected end to end in turn to form a zigzag polyline, and then the front and tail of the polyline are connected with a line segment to form a closed polygon, the direction of the line segment is from the beginning of the polyline to the tail, then the length of this line segment is the size of the resultant force, and the direction of the slide bucket of the line segment is the direction of the resultant force.

For any two forces f1, the resultant force of f2.

For any case: it can be found according to the cosine theorem.

That is, f = f1 2+f2 2+2f1f2cos is the angle between the two forces.

For two forces in the same line, you can find them with an algebraic sum.

f = f1 + f2

Conventional methods in high school physics.

Orthogonal decomposition. If you have any questions, please ask.

Mathematical formulas?

Yourself.

If I have learned triangles, it is just right.

Vector. Follow the parallelogram principle.

1.The resultant force can be found directly using the parallelogram rule (triangle rule)2It is possible to use the orthogonal decomposition method.

That is, to establish a Cartesian coordinate system.

Put the components along the horizontal axis.

The vertical axis decomposes the sedan ruler tremor, and then establishes the equilibrium equation and solves it. This method is suitable for situations where multiple sub-trap circles strive to join forces.

3.For two components that are at an angle to each other, the sum of the flat and closed sides of the two resultant forces under the root of the resultant force f is the cosine of the product of the two components that are twice the force.

The sum of values.