"Scientific Inquiry: The Synthesis of Forces" Force and Balance PPT (the second lesson explores the rules of the synthesis of two forces at angles to each other)

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"Scientific Inquiry: The Synthesis of Forces" Force and Balance PPT (the second lesson explores the rules of the synthesis of two forces at angles to each other)

Part One: Clarify the Principles

1. Experimental purpose

1. Explore the relationship between two common point forces at an angle to each other and their resultant force.

2. Learn to use the idea of ​​​​equivalence to explore vector synthesis methods.

2. Experimental equipment

Wooden board, rubber band, thin wire, spring dynamometer, thumbtacks, white paper, pencil, scale, set square.

3. Experimental Principle and Design

Let two common point forces F1 and F2 at an angle to each other act on an object and produce obvious effects. Then use a force F to replace F1 and F2 to produce the same effect. Measure F1, F2 and F, compare their sizes and directions, and find out the rules.

4. Experimental steps

1. As shown in Figure (a), on a wooden board covered with white paper, fix one end of the rubber band to point A with a thumbtack, and tie the other end to a node B with two thin wires. Hang the dynamometer on the two thin wires.

2. As shown in Figure (b), pull the two dynamometers respectively, use a pencil to mark the stretched position of node B, mark it as point O. Write down the indications F1 and F2 of the two force gauges at this time, and mark the direction of the force along the two thin lines.

3． As shown in Figure (c), pull a dynamometer with force, and also pull node B to O. Write down the indication F of the dynamometer at this time, and mark the direction of the force along the thin line.

4. Use force diagrams to draw F1, F2 and F.

5. Data analysis

1. Construct a parallelogram with F1 and F2 as adjacent sides, and draw the diagonal F′.

2. Compare the magnitude and direction of F′ and the resultant force F to see whether they are equal in magnitude and direction within the error range.

6. Experimental conclusion

F′ and the diagonal F coincide within the error range, which means that when two forces are combined, use the line segments representing the two forces to construct a parallelogram for the adjacent sides, then the force represented by the diagonal of the parallelogram is the resultant force.

7. Error analysis

1. If a standard spring dynamometer is not selected, or the two spring dynamometers are not tested against each other in the experiment, this will cause system errors.

2. If the rubber strip, string and wooden board are not parallel, then the position of node O and the direction of the two strings recorded on the white paper are the projection of the actual node and string on the white paper, causing experimental errors.

3． The two strings are too short. If you record the direction of the strings by first tracing two points and then connecting the lines, there will be a large deviation, which will also affect the direction and magnitude of the resultant force.

4. Experience shows that the angle between the two component forces F1 and F2 cannot be too large. The larger the angle θ is, the smaller the resultant force will be under the same situation. The error of the resultant force calculated by drawing a parallelogram will be greater. The difference between F and F′ The deviation is also greater.

5. If the drawing is not rigorous, such as the parallel lines are not parallel, the force diagram, magnitude and direction are not accurate, etc., it will cause accidental errors.

8. Precautions

1. Use of spring dynamometer

(1) The two spring dynamometers should be calibrated to zero before use, and the range and minimum scale unit should be checked.

(2) When using a spring dynamometer, it should be parallel to the plate surface, and the direction of the pulling force should be along the axis of the spring.

(3) When reading, the line of sight should be facing the scale plate of the spring dynamometer, and at the same time, pay attention to estimating to the next digit of the minimum scale.

2. Measures to reduce errors

(1) The knots of the rubber strip should be smaller and the string (set) should be longer.

(2) When using two spring dynamometers, the angle between the two pulling forces should be appropriately large.

(3) Under the conditions that the resultant force does not exceed the spring force measuring range and the deformation of the rubber strip does not exceed the elastic limit, the pulling force should be made as large as possible to reduce the error.

(4) In the same experiment, the position of node O must remain unchanged after the rubber strip is stretched.

Synthesis of scientific inquiry power PPT, part 2: interpretation of typical examples

Experimental principles and operations

(2019•Luoyang Grade 1 Test) In the experiment of "Exploring the synthesis law of two forces at an angle to each other", a student used thumbtacks to fix the white paper on a horizontally placed wooden board, and fixed one end of the rubber strip at a point on the board , two string sets are tied to the other end of the rubber strip. Use two spring dynamometers to pull the two string sleeves respectively, and apply tension at an angle to each other, so that the rubber strip stretches and the node reaches a certain position on the paper, as shown in the figure. Please complete the following experimental operations and processing:

(1) Use a pencil to trace the node position and mark it as O;

(2) Record the readings F1 and F2 of the two spring dynamometers, use a pencil to trace several points along the direction of each string (set), and use a scale to connect the corresponding points into lines;

(3) Only use a spring dynamometer, pull the node of the rubber strip to position O through the string sleeve, and record the reading F3 of the dynamometer.

__________________________________________________;

(4) According to the requirements of the force diagram, make the pulling forces F1, F2, and F3;

(5) Determine the resultant force F of F1 and F2 according to the parallelogram rule of force;

(6) Compare the consistency of ________. If there is a big difference, analyze the reasons and make corresponding improvements before conducting the experiment again.

Processing and analysis of experimental data

In the experiment of "exploring the method of finding the resultant force", there are wooden boards, white paper, thumbtacks, rubber bands, string sets and a spring scale.

(1) In order to complete the experiment, a student found another spring and first measured its stiffness coefficient. The experimental data obtained are as follows:

(2) In a certain experiment, the pointer position of the spring scale is as shown in Figure A, and its reading is ________N; at the same time, the obtained k value is used to obtain the elastic force value on the spring as 2.50 N. Please draw these two common values ​​in Figure B. The resultant force F of the point forces;

(3) From the figure, we get F+=________N.

Experimental improvement and innovation

A classmate tried to explore the synthesis law of two mutually angled forces 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: hang one end of two rubber bands on two nails A and B on the wall, and connect the other end to a third rubber band with the node O. A heavy object is hung from the other end through a string, as shown in the picture.

(1) (Multiple choice) 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 adopted is ____________________________.

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For more information about the PPT courseware "Force and Balance explores the synthesis law of two forces at an angle to each other and scientifically explores the synthesis of forces", please click Force and Balance PPT to explore the synthesis law of two forces at an angle to each other PPT scientifically explores the synthesis of forces PPT labels.

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Update Time: 2024-11-20

This template belongs to Physics courseware Lu Ke Edition High School Physics Compulsory Course One industry PPT template

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