"The Relationship between Acceleration, Force and Mass" Newton's Laws of Motion PPT courseware

Description

"The Relationship between Acceleration, Force and Mass" Newton's Laws of Motion PPT courseware

Part One: Experimental Basics

Purpose

1. Explore the relationship between acceleration, force and mass.

2. Learn to use the control variable method to explore physical laws.

experiment equipment

Wooden board with fixed pulley, thin pad, trolley, string, weight (small hook or sand bucket), dotting timer, paper tape, AC power supply, balance, weights, scale.

Experimental principles and design

1. The basic idea of ​​the experiment - controlled variable method

(1) Keep the mass of the car unchanged, change the pulling force F acting on the car by adding or removing weights, and measure the corresponding acceleration a of the car. The relationship between a and F can be obtained.

(2) Keep the pulling force F constant, change the mass m of the trolley by adding or subtracting weights on the trolley, and measure the corresponding acceleration a of the trolley. The relationship between a and m can be obtained.

2. Key points in experimental design - measuring the net external force of the car

(1) The end of the wooden board without pulleys is raised, and the component of gravity along the inclined plane of the car offsets the friction and other resistances of the car.

(2) The mass of the hung heavy object is much smaller than the mass of the car, and the gravity of the heavy object is approximately equal to the total external force on the car.

Experimental steps

(1) Place the trolley on a wooden board with fixed pulleys, pass the paper tape through the dotting timer and hang it on the rear of the trolley.

(2) Use a thin pad to raise one end of the board, and adjust its inclination until the points printed by the dot timer on the paper tape are evenly distributed when the car is moving.

(3) Hang a heavy object on one end of the string, and tie the other end to the front end of the car through a fixed pulley. Note that the mass of the heavy object should be much smaller than the mass of the trolley.

(4) Put the car close to the dotting timer and start the dotting timer, and then release the car from standstill. The dot timer marks a series of dots on the paper tape, from which the car's acceleration is calculated. Keep the mass of the trolley unchanged, increase the mass of the heavy object (the total mass of the heavy object is still much smaller than the mass of the trolley), repeat the experiment, and record the different pulling forces on the trolley and the corresponding calculated acceleration.

(5) Keep the weight unchanged, increase or decrease the weight on the trolley to change the mass of the trolley, repeat the experiment, and record the mass of the trolley and the corresponding acceleration.

data analysis

(1) When the mass m of the trolley is constant, fill in the experimental data of the tensile force F and the corresponding acceleration a in Table 1; when the tensile force F is constant, fill in the experimental data of the mass m of the trolley and the corresponding acceleration a in Table 2.

Experimental results

Analyze the data and images and get the experimental conclusions:

1 For the same object, when m remains unchanged, a and F are proportional.

2 For different objects, when F remains unchanged, a and m are inversely proportional.

PPT on the relationship between acceleration and force and mass, part 2: experimental test points

Test Point 1 Experimental Principles and Operations

[Typical Example 1] Use the device as shown in the figure to study the relationship between the acceleration a of the car and the mass M of the car when the force F is constant. The experimental steps designed by a certain student are as follows:

A. Use a scale to weigh the mass of the trolley, the bucket and the sand inside;

B． Install the experimental equipment according to the diagram;

C. Tie a light rope to the trolley and hang the sand bucket around the fixed pulley;

D． Connect the electromagnetic dotting timer to the 6 V battery, turn on the power, let go of the car, the dotting timer will mark a series of dots on the paper tape, and mark the mass M of the car on the paper tape;

E. Keep the mass of the bucket and the sand in it unchanged, increase the number of weights on the trolley, record the M value after each increase, and repeat the above experiment;

F. Analyze each strip of paper, measure and calculate the acceleration value;

G． Make aM relationship image, and determine the relationship between a and M from the image.

(1) The important experimental step that the student missed is ________, and this step should be ranked after the ________ experiment.

(2) In the above steps, the error is _________, so ____________________ should be changed to ____________________.

(3) In the above steps, the inappropriate processing is __________, and ________ should be changed to ________.

[Key Points]

Three Points About Balancing Friction

(1) Place a thin wooden board under one end of the wooden board without a fixed pulley, and repeatedly move the position of the thin wooden board until the paper belt can move at a uniform speed on the wooden board when no heavy objects are hung on the trolley.

(2) The way to judge whether the friction force is completely balanced is to see whether the dots printed by the dot timer on the paper tape are evenly spaced. If the dots are evenly spaced, it means that the car is moving at a constant speed, and the friction force is completely balanced.

(3) Balanced friction means that the component of gravity along the inclined plane on the car is equal to the resistance on the car, that is, mgsin θ = μmgcos θ. m on both sides of the equation can be eliminated, so after balancing the friction, no matter how much weight is changed, There is no need to rebalance the friction force whether the mass of the object or the mass of the car is changed.

[Point-to-point training]

1. (1) We already know that the acceleration a of an object is related to two factors: the combined external force F and the mass m. The way of thinking to study the quantitative relationship between these three physical quantities is ______________.

(2) A student’s experimental plan is as shown in the figure. She wanted to use the gravity of the sand bucket to represent the total external force F on the car. In order to reduce the experimental error caused by this approach, she first made two adjustments:

a. Use small wooden blocks to raise the end of the long board without pulleys for the purpose of __________________________________________________.

b. Make the total mass of the sand bucket much smaller than the mass of the trolley, so that the force pulling the trolley is approximately equal to ______________.

(3) When the student uses the paper tape produced in the experiment to find acceleration, there are two solutions:

A. Calculate using the formula a=2xt2;

B． Use the difference-by-difference method to calculate according to a=ΔxT2.

Of the two options, do you think the option ________ is more reasonable?

Test Point 2 Data Processing and Error Analysis

[Typical Example 2]The experimental device for "exploring the relationship between acceleration, force and mass" is shown in the figure.

(1) The following statement is correct ________.

A. Every time you change the mass of the trolley, the friction should be rebalanced

B． During the experiment, the car should be released first and then connected to the power supply.

C. The mass of this experimental weight and weight plate B should be much greater than the mass of trolley A

D． When using images to explore the relationship between acceleration and mass, a1mA images should be used

(2) In the experiment, a student typed out a piece of paper tape as shown in the picture. He selected several timing points as counting points. There were 4 timing points that were not marked between two adjacent counting points, among which s1=7.06 cm, s2=7.68 cm, s3=8.30 cm, s4=8.92 cm. It is known that the frequency of alternating current is 50 Hz, then the acceleration of the paper tape is ______ m/s2. (Keep two significant figures)

(3) A classmate raised the right end of a long wooden board appropriately for the purpose of ____________. But he raised the right end of the long board too high, causing the angle to be too large. Let a represent the acceleration of the car, and F represent the pulling force of the thin wire on the car. The picture of the aF relationship he drew is ________.

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For more information about the PPT courseware "Newton's Laws of Motion: The Relationship between Acceleration and Force and Mass", please click the Newton's Laws of Motion ppt: The Relationship between Acceleration and Force and Mass ppt tag.

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Update Time: 2024-10-03

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