"Exploring the law of synthesis of two forces at an angle to each other" Force and Balance PPT

Description

"Exploring the law of synthesis of two forces at an angle to each other" Force and Balance PPT

The first part of the content: [Learning literacy·clear goals]

Scientific inquiry: 1. Verify the parallelogram rule for the synthesis of two forces at an angle to each other. 2. Further use the graphing method to find the resultant force of two forces at a common point.

Explore the synthesis law of two forces at an angle to each other PPT, the second part of the content: independent preview to explore new knowledge

1. Experimental principles and methods

The action effect of one force F′ and the action effect of two forces F1 and F2 can make the rubber strip fixed at the same end extend to the same point O, then F′ must _____ with the resultant force of F1 and F2, so F1, F2 Draw a parallelogram for the adjacent sides to find the resultant force F, and compare the ________ of F' and F to verify the parallelogram rule when the two common point forces forming an angle with each other are combined.

2. Experimental equipment

Square wooden board, white paper, spring dynamometer (two), triangle plate, scale, thumbtacks (several), thin-core pencil, rubber strip, string (two), etc.

3. Experimental steps and data processing

1. Installation of the instrument: Use thumbtacks to nail the white paper to the square wooden board on the horizontal table, and use thumbtacks to fix one end of the rubber strip at point A. Tie two string sets to the other end of the rubber strip, as shown in the picture.

2. Operations and Records

(1) Use two spring dynamometers to hook the string sets respectively, pull the rubber strip at an angle to each other, so that the rubber strip stretches, and the node reaches a certain position O, record the readings of the two spring dynamometers, and use a pencil to Trace the position of point O and the direction of the two string sets at this time.

(2) Use a spring dynamometer to pull the node of the rubber strip to the same position O through the string sleeve, and record the reading of the spring dynamometer and the direction of the string sleeve.

3. Charting and analysis

(1) Use a pencil and a scale to draw a straight line from node O along the direction of the two string sets. Draw a diagram of the readings F1 and F2 of the two spring dynamometers according to the selected scale, and use F1 and F2 As the adjacent side, use a scale to draw a parallelogram, and draw the diagonal line of the parallelogram through point O. This diagonal line is the diagram of the resultant force F.

(2) Use a scale to draw the same scale from point O along the recorded direction.

The diagram of the tension force F′ using a spring dynamometer is as shown in the figure.

(3) Compare the force F′ with the resultant force F calculated using the parallelogram rule. Within the allowable error range, whether the magnitude and direction are the same.

(4) Change the magnitude and angle of the two forces F1 and F2, and repeat the above experiment twice.

4. Error analysis

5. Things to note

1. How to select a spring dynamometer: Adjust the two spring dynamometers to zero and then hook each other and pull them horizontally. If the two springs have the same reading during the pulling process, choose another one; if the readings are different, choose another one until Until the same.

2. Method to ensure that the effect of component force and resultant force is the same: in the same experiment, the position of node O must be the same when the rubber strip is stretched.

3. How to check the aging of the rubber strip: Use a spring dynamometer to pull the rubber strip. Repeat this several times until the rubber strip reaches the same length and see if there is any change in the reading of the spring dynamometer.

4. Angle range of the spring dynamometer: When using two spring dynamometers to hook the string sets and pull the rubber strip at an angle to each other, the angle should not be too small or too large, between 60° and 120°. should.

5. The principle of selecting the tensile force: make the tensile force appropriately larger without exceeding the range of the spring dynamometer and the deformation limit of the rubber strip.

6． Precautions for drawing force diagrams: In the same experiment, the scale selected for drawing force diagrams should be the same, and the scale should be selected appropriately so that the force diagram is slightly larger.

Exploring the synthesis law of two forces at an angle to each other PPT, the third part of the content: cooperative exploration to overcome difficult problems

[Example 1] When doing the experiment of "exploring the method of finding the resultant force":

(1) In addition to the existing equipment (square wooden board, white paper, spring dynamometer, string, scale, thumbtacks and pencil), there must also be ________ and ________.

(2) In order for each resultant force and component force to produce the same effect, ()

A. Pull the rubber strip to the same position every time

B． Straighten the rubber strip every time

C. Accurately read the reading of the spring force gauge every time

D． Remember the direction of the string every time

(3) In order to improve the accuracy of the experiment and reduce the error, what should be paid attention to during the experiment?

(4) In the experiment of "exploring the method of finding the resultant force", the experimental results of a certain student are as shown in the figure, where A is the thumbtack that fixes the rubber strip, and O is the position of the node between the rubber strip and the string. In the figure, ________ is the theoretical value of the resultant force of forces F1 and F2; ________ is the experimental value of the resultant force of forces F1 and F2. Verify the parallelogram rule by comparing ________ with ________.

[Analysis](1) According to the requirements of the experimental equipment, rubber strips and triangular plates (used to make parallelograms) are also necessary.

(2) According to the experimental principle, the correct option is A.

(3) During the experiment, attention should be paid to: ① Use a string with low elasticity; ② The axes of the rubber strip, string and spring dynamometer should be on the same plane and parallel to the board surface, etc.

(4) In this experiment, the resultant force F made according to the parallelogram rule is the theoretical value of the resultant force of F1 and F2, and the force F′ measured when pulling with a spring dynamometer is the experimental value of the resultant force of F1 and F2 value. By comparing the sizes and directions of F and F′, the parallelogram rule can be verified.

[Example 2] A classmate tried to verify the parallelogram rule of force at home. He found three identical rubber bands (following Hooke's law) and several small weights, as well as a scale, a triangle, a pencil, a string, a white paper, Nails, the following experiment was designed: As shown in the figure, one end of the two rubber bands is hung on the two nails A and B on the wall, and the other end is connected to the third rubber band. The node is O. A heavy object is hung from the other end of the three rubber bands through a string.

(1) In order to complete the experiment, the following operations are necessary________.

A. Measure the length of the string

B． Measure the original length of the rubber band

C. Measure the length of the rubber band after hanging the weight

D． Record the position of node O after hanging the weight

(2) The position of the nail is fixed. If you want to use existing equipment and change the conditions to verify again, the method that can be used is_______________________________.

[ Analysis Find the position of node O behind the object, and note the directions of the three rubber bands at the same time to determine the direction of each pulling force, and draw a diagram of the resultant force according to the parallelogram rule. Therefore, the required operations are B, C, D.

(2) To change the conditions and verify again, you can use the method of replacing different small weights.

Exploring the synthesis law of two forces at an angle to each other PPT, the fourth part of the content: Class drills to improve literacy

1. The experimental principle of "exploring the method of finding the resultant force" is the equivalence principle, and its equivalence refers to ()

A. Make the spring dynamometer undergo the same deformation in the two situations

B． Make the two components and the resultant force satisfy the parallelogram rule

C. Make the two rubber bands stretch by the same length

D． Make the knots of the two rubber bands and the two rope sets coincide with point O

D. In the experiment of “exploring the method of finding the resultant force”, when the rubber band is stretched twice, the length and direction of elongation are the same, so the effect of the two components of force and the resultant force are the same, and they are equal. There is an effective substitution relationship, so C is wrong and D is correct; during the experiment, the magnitude and direction of the pulling force of the spring dynamometer can be changed, A is wrong; the resultant force and the component force must satisfy the parallelogram rule and are not caused by humans. Therefore B is wrong. ]

2. In the "Verification of the Parallelogram Rule of Forces" experiment, one end of the rubber strip needs to be fixed on a horizontal wooden board, and two strings should be tied to the other end. The other ends of the strings have rope sets (as shown in the picture). In the experiment, two spring dynamometers are used to hook the rope sets respectively and pull the rubber strip at an angle to each other. A classmate believes that the following items must be paid attention to during this process:

A. The two strings must be of equal length

B． The rubber strip should be on the same straight line as the bisector of the angle between the two ropes.

C. When using the spring dynamometer, make sure the spring dynamometer is parallel to the plane of the board.

The correct one is ()

C: This experiment verifies that the effect of the two component forces is equivalent to the effect of the resultant force. It does not require that the two component forces are equal, so B is wrong; it has nothing to do with the length of the two ropes, A is wrong; but it needs to make the two component forces equal to The resultant forces are in the same plane, so C is correct. ]

3. When a student did the experiment of "exploring the method of finding the resultant force", the main steps were:

A. Place a square wooden board on the table, lay a piece of white paper on the square wooden board, and nail the white paper to the square wooden board with thumbtacks;

B． Fix one end of the rubber strip to point A on the board with a thumbtack, tie two strings to the other end of the rubber strip, and tie a noose to the other end of the string;

C. Use two spring dynamometers to hook the rope sets respectively, pull the rubber strip at an angle to each other, so that the rubber strip stretches, and the node reaches a certain position O. Record the position of point O and read out the two spring dynamometers. indication;

D． According to the selected scale, use a pencil and a scale to draw diagrams of the pulling forces F1 and F2 of the two spring dynamometers, and use the parallelogram rule to find the resultant force F;

E. Use only a spring dynamometer, pull the rubber strip through the string sleeve to extend it, read the spring dynamometer indication, note the direction of the string, and draw a diagram of the force F' on the same scale. ;

F. Compare the sizes and directions of F′ and F to see if they are the same and draw conclusions.

In the above steps:

(1) The serial numbers of the steps with important omissions are ________ and ________;

(2)The missing contents are __________ and ____________ respectively.

[ Analysis

(2) The directions of the two strings are not recorded in C, and it is not stated in E whether the knots of the rubber strips are pulled to the same position O.

Keywords: Free download of the PPT courseware of Lu Ke Edition High School Physics Compulsory Course One, exploring the synthesis law of two mutually angled forces PPT download, force and balance PPT download, .PPT format;

For more information about the PPT courseware "Force and Balance Exploring the Synthetic Law of Two Forces at Angles to Each Other", please click the Force and Balance ppt Exploring the Synthetic Law of Two Forces at Angles to Each Other ppt tag.

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Update Time: 2024-11-21

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