Physics experiment questions in the second year of junior high school, and physics experiment questi

Fill in the blanks m2 - m1

m1-m2）/v

1) Scheme 1: When the edible oil in the beaker is poured into the graduated cylinder, some of the oil will not be clean; The measured volume of edible oil is on the small side; It will increase the experimental error.

Scheme 2: The shortcomings of scheme 2: Before adjusting the balance nut in step (1), the free code is not adjusted to the zero engraved line. Prepare option 1: add one step before step (4); Measure the total mass of the beaker and the unfinished cooking oil.

2) Prepare to choose scheme 2: After the balance is placed on the water platform in step (1), adjust the travel code to the zero marking position, and then adjust the balance nut to balance the beam.

Scheme 1: In step (3), when the cooking oil in the beaker is poured into the graduated cylinder, some of the oil will not be cleanedIn step (3), when the cooking oil in the beaker is poured into the graduated cylinder, some of the oil will not be clean.

Scheme 2: Before the adjusting balance nut in step (1), the free code is not dialed to the zero scale, and the free code is not dialed to the zero scale before the adjusting balance nut in step (1).

2) You're ready to choose a plan.

Two-two. To do the experiment In order to successfully complete the experiment, the shortcomings in the scheme should be changed to (1) after the balance is placed on the water platform, the free code is first adjusted to the zero scale line, and then the balance nut is adjusted, so that the balance in the beam balance (1) is placed behind the water platform, the free code is adjusted to the zero scale line first, and then the balance nut is adjusted to make the beam balanced.

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Problem description:1Method: Put a raw egg in a cup of water, then gradually add salt to the water and dissolve it, pay attention to what happens, and ask questions about this phenomenon.

2.Method: Carefully pour water and cooking oil (one small glass each) along the walls of the cup into a deep glass, and then add a grape or a small candle to observe the phenomenon and ask questions.

I did, but I didn't find anything, I'm new to the subject of physics, please help, thank you.

Analysis: Experiment 1: Eggs will sink to the bottom of the cup when placed in clean water, because the density of eggs is greater than that of water, put salt in the water until saturated If there is no phenomenon, the density of concentrated brine is still not as large as that of eggs.

Experiment 2: Slowly pour water and cooking oil into the cup, you can find that the water is under the oil, because the density of water is greater than that of oil, and then put in a candle or grapes, it will also sink, but the speed of sinking in the oil layer and the water layer is different!!

Question 1: 1Measure the gravity of the metal block g1 and find the mass of the metal block m=g1 g2Fill the beaker with water. Gravity g2 is measured

3.When the metal block is submerged in a beaker, it will expel water. At this point, the force g3 exerted on the metal block in the water is measured.

4.The buoyancy force of the metal block f floats = g1—g3 (or the beaker water gravity g4 is measured after taking out the metal block).

5.The gravity of the discharged water is g row = f float ( or g row = g2—g4)6Find the mass of water m = g and drain g

7.Find the volume of water v=m The density of water (note the unit)8The volume of water is equal to the volume of the metal block.

9.The density of the metal = the mass of the metal The volume of the metal.

Question 2: Measure the volume of a metal according to the method used in question 1.

Put the metal block into a full beaker of coke After comparing the number of views before and after, the mass of the cola is calculated and the volume of the row is equal to the volume of the metal block There is volume There is mass Isn't it very simple to find the density Hehe.

1) Use a spring dynamometer to measure the gravity in the air first, convert and calculate the mass and then measure the gravity in the water, and calculate the gravity difference between the two times to calculate the volume and calculate the density of the small metal block 2) Use the spring dynamometer to measure the gravity in the air first, then measure the gravity in the water, and then put the small metal block into the cola, and calculate the answer according to the buoyancy ratio equal to the density ratio of water and cola.

Design experiment: equipment: fish tank (with water, fish), newspaper.

Steps: Wrap the newspaper around the fish tank, pat the table and observe the fish's reaction.

Phenomenon: When the table is slapped, the fish swims around.

Conclusion: Liquids can transmit sound

Hehe, that's the standard answer, I've done it.

If there is anything you don't understand in the future, you can come and ask me oh o( o

As long as the water can vibrate, it can make sound. Put a motor in the water, close the cover, turn on the motor and listen to the sound.

Also, use a drop of water from a high place to drop into a tank filled with water and hear a sound.

6 hooks of the same quality; 1 scale.

Stand the scale upright on the right side of the pulley block unit.

Hang 1 hook code under the movable pulley in turn, pull the rope end with a spring dynamometer, pull up vertically and slowly and at a constant speed to rise a distance, record the rope end moving distance S and the hook code moving distance H respectively, and record the quality m of the hook code and the indicator F of the spring dynamometer in **.

Hang 2, 3, 4, 5, 6 hook codes sequentially under the movable pulley, repeat the steps and record the total mass m of the hooked code each time and the indication f of the spring dynamometer in ** respectively.

Using the formula =w has w total = mghfs to calculate the hook code of six lifts of different weights, the mechanical efficiency of the pulley block is 1, 2, 3....6, and record the data in **

Same pulley set, hook code, spring dynamometer.

First, the gravity of a hook code is measured with a dynamometer, the hook code is hung on the pulley block, and the tensile force is measured by pulling the pulley block in a straight line at a uniform speed with a dynamometer to calculate the mechanical efficiency;

Then use the dynamometer to measure the gravity of the two hook codes, hang the hook code on the pulley block and pull the pulley block with the dynamometer at a uniform speed to measure the tensile force, and calculate the mechanical efficiency; to compare.

One: f r = (f + l) r

fr=fr+lr

f(r-r)=lr

f=lr/(r-r)

2: Reason 1: The plane mirror is an illusion of equal size and erection.

Reason 2: Use the eyes to see the image directly, since the eye is a convex lens, when the image is real, the farther the object is from the convex lens, the smaller the image on the retina.

This is a human delusion).

Three: see figure.

The method of imaging the first plane mirror is adopted.

Xiaomi uses the eye to see the image directly, because the eye is a convex lens, when forming a real image, the farther the object is from the convex lens, the smaller the image on the retina; Conversely, the larger.

Topic 1, equipment: hard rod, object B (known density is Pb), object A, a certain liquid of unknown density, scale, thin wire, beaker, measurement of liquid density.

Let the density of the liquid to be measured be Pa (Pa should be less than Pb, otherwise there is no solution).

1. Use a beaker to hold an appropriate amount of liquid a, and measure the height of the liquid with a scale to l0; Put object B into liquid A, press B from above with a virtual hard rod, so that B is completely immersed in A, and measure the liquid height to L1.

The volume of the available object b is.

vb=s（l1-l0）

2. Fill a beaker with liquid A, and measure the height of liquid with a scale to L2; If object B is placed in liquid A, and part B is immersed in A, then the liquid will overflow; Take out b and measure the height of the remaining liquid in the beaker to L3.

The buoyancy force on object b is .

pb*vb=pa*s（l2-l3）

Pa= PB*vb S(L2-L3)= Pb* S(L1-L0) S(L2-L3)= Pb*(L1-L0) (L2-L3).

Topic 2, equipment: large container, plastic bucket, object A (density greater than water), sufficient amount of water, scale, Minna to measure the density of A.

These devices cannot measure the density of a, but only the volume of a, as shown in question 1. Doubt is missing the scales.

1 The heat absorbed by the same substance at the same temperature is proportional to its mass.

2 The ratio of heat absorbed to mass by the same substance at different temperatures is different.

3 Tables 1 and 3.

4 The ratio of absorbed heat to increased temperature is different.

1. The temperature is the same, and the greater the mass, the more time it takes.

2.proportional.

After a student "what is the relationship between the trunk current and the current of each branch in the parallel circuit", he imagined whether he could complete the experiment with only one ammeter and only one wire? (The current through the bulb is known to be about.) Can you confirm his assumption?

1) The equipment and quantity required ---

2) Experimental procedure: --

3) Please evaluate this improvement: --

Answer: Prepare a switch for a light bulb; 1A ammeter, 1 pcs; Conducting wire.

1. Connect a parallel circuit, install an ammeter in the trunk circuit, and install switches and bulbs in each branch.

2. Connect the power supply, connect each branch in turn, connect one branch at a time, and record the reading of the ammeter.

You can get: a light bulb --- current; Two bulbs --- current; Three bulbs --- currents.

3. The sum of the current of each branch in the parallel circuit is obtained.

While doing the experiment of "observing the boiling of water", A. Second. The students in Group C and Group C each chose one of the two sets of equipment to complete the experiment

Second. Although the two groups of students chose the same experimental setup, the time when the water began to boil was different, and the boiling image they drew is shown in Figure C: the reason for the difference between the two images A and B is that the water is different.

Answer 1 The quality of the water.

2 A seems to have no lid on the beaker b There is a lid on the beaker, so the pressure in the beaker is different.