"Scale of Objects and Their Measurement" Scale, Mass and Density of the Material World PPT Courseware 3

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"Scale of Objects and Their Measurement" Scale, Mass and Density of the Material World PPT Courseware 3

1. Measurement of length

1. Unit

①The length is represented by the symbol _____.

②In the International System of Units, the unit of length is _____, represented by the symbol _____.

In addition to rice, there are:

Kilometers km, decimeters dm, centimeters cm,

Millimeters mm, microns μm, nanometers nm.

2. Unit conversion

1km=10³ m =1000m

1dm=1/10m = 0.1m

1cm=1/10²m =0.01m

1mm=1/10³m =0.001m

1μm=1/106m

Remember the "ruler" on your body

①The adult waist is about 1_____;

②The width of the palm is about 1 _____;

③The width of one finger is about 1_____.

Know your own "ruler"

Normal people hold their hands flat, and the distance between the tips of the left and right middle fingers is approximately equal to the distance from the top of the head to the soles of the feet.

unit exercises

The diameter of a table tennis ball is 3.5 ( )

A new piece of chalk is 10 ( ) long

A pencil is 18 ( ) long

The diameter of a hair is about 100 ( )

One floor height 3.0 ( )

The thickness of a coin is about 2.5 ( )

4. Use measuring tools correctly

① Use the first three to look at: zero, range, and graduation.

② Three places during operation: along the line, close to, and zero.

③ Pay attention to three things when reading: vertical, estimated reading, and unit.

practice

Measure the width of your physics textbook

A centimeter scale measures the width of a physics textbook ______.

A millimeter scale measures the width of a physics textbook ______.

2. Measurement of length

5. Error

①There will always be some difference between the measured value and the true value of the measured object. This difference is called _____.

②Cause of error: related to the person measuring

Related to measuring tools

③Mistakes can be avoided. Errors are inevitable

④Methods to reduce errors: __________.

In addition, choosing higher precision measuring tools or improving measurement methods can also reduce errors.

Special methods of length measurement

1. Turn the curve into a straight line

Suitable for measuring the length of short curves, such as the length of railway lines on maps

2. Equivalent substitution method

Suitable for measuring the height of cones and diameter of cylinders

3. Cumulative average method

Suitable for measuring the thickness of a piece of paper and the diameter of thin copper wire

4.Roller method

Suitable for measuring the length of longer curves, such as the perimeter of flower beds

2. Measurement of volume

1. Know the common units of volume and liquid volume;

2. Be familiar with the measuring cylinder and the scale on the measuring cylinder;

3. Learn to use a measuring cylinder to measure the volume of liquids and irregularly shaped solids;

4. Can use a measuring cylinder to measure the volume of liquid.

Precautions when using measuring cylinder

1. See its measurement range and minimum scale clearly

2. The measuring cylinder must be placed flat on a horizontal table before measurement.

3. When most liquids are at rest, the liquid surface is concave in the measuring cylinder.

4. When reading, the line of sight should be level with the lowest point in the center of the concave liquid surface.

Looks too small when looking up; looks too big when looking down

Measurement of the volume of small irregular objects that are insoluble in water

①First measure a certain amount of water V1

②Put the object to be measured out of the water and measure the volume V2

③The difference between the two is the volume V of the object to be measured.

④V = V2 - V1

1. Irregular objects can be measured with water. If you want to measure the volume of rock sugar, how to measure it?

You can use fine sand or flour instead of water, or you can use insoluble liquids, such as oil

2. How should floating solids be measured?

Acupressure

1. When using a measuring cylinder to measure volume, which of the following statements is incorrect ( )

A. Place the measuring cylinder flat on the table

B． To understand the measuring range and minimum scale of the measuring cylinder

C. A graduated cylinder can only measure the volume of liquids, not solids.

D. When the liquid level is concave in the measuring cylinder, the line of sight should be level with the lowest point in the center of the concave liquid level.

2. The volume of a bottle of mineral water is 500 _____.

3. When measuring the volume of a liquid with a graduated cylinder, if the line of sight is looking down, the measured volume will be ( ) larger than the real volume of the liquid.

A. Bigger B. Smaller C. Same big D. All three of the above are possible

4. Accurately measure 70 ml of sodium chloride solution. The correct graduated cylinder is ( )

A.100ml B.50ml C.200ml D.10ml

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Update Time: 2024-11-24

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