Find a strong man to do two physics experiment questions junior high school students .

Problem 1: First call the metal mass m1

Then weigh the mass of the filled cup with water m2

Put the metal in a water cup and weigh the total mass m3

Then the mass of the discharged water is m1+m2-m3

If the density of water is known, the volume of drained water, that is, the volume of metal, can be obtained.

The final expression is m1*p water (m1+m2-m3) Problem 2: Measure the length a and width b of the metal sheet, fold the metal sheet to the extent that it can be placed in the balance tray, and measure the mass m

The thickness is m (p*a*b).

Question 1: 1, first pour out some of the water in the beaker (to ensure that the water will not overflow when the metal is put in), record the volume of water V water in the beaker, and then measure the m water through the balance;

2. Put the metal bag into the beaker, and then record the volume v water + metal at this time; Then measure the m water + metal at this time through the balance;

3. From this, we can calculate v metal box m metal, and calculate the metal density by m v: = m water + metal - m water v water + metal - v water.

Question 2: 1. Use a millimeter scale to measure the length of gold foil a meter and the width of b m, and calculate the area of gold foil;

2. Measure the mass of gold foil m kg with a balance;

3. The height of the gold foil can be calculated by mv h=m abm.

(1) Prevent heat loss and shorten the heating time.

2) The volume becomes larger (the depth is constantly decreasing, and the pressure is constantly decreasing) (3) Because the specific heat of the container is less than the specific heat of the water, absorbing the same heat, the temperature of the container is higher, so there is a temperature difference between the water and the container after the alcohol lamp is turned off, and the water continues to absorb heat and boil for a period of time.

The watchtower lord adopts!

33 (9 points) In the experiment of measuring the electric power of a small bulb with a rated voltage, the circuit is shown in Figure A, (1) A student closes the switch after connecting the circuit correctly, and finds that the bulb does not light up, the ammeter has no indication number, and the voltage indication number is equal to the power supply voltage, and the fault may be the bulb open circuit.

2) After troubleshooting, when moving the slide p to a certain position, the voltage representation number is shown in Figure B, to measure the rated power of the small bulb, the slide p should be moved to the optional "a" or "b") end of the b.

3) move the slider p, write down the indication of multiple groups of corresponding voltmeters and ammeters, and draw the i u image shown in figure c, according to the image information, the rated power of the small bulb can be calculated is w. Do the math yourself.

4) If the ammeter is broken, there are a number of single-pole single-throw switches on the experimental table, and the resistance value is a fixed value resistor, which can be used, and the resistance of 5 should be selected to measure the rated power of the small bulb, please draw the circuit diagram, and write out the steps and expressions (not dismantling the circuit in the experimental measurement).

Measure the gravity of that part of the nut.

The gravitational force of the vial is:

The buoyancy experienced by the vial.

Take out the nut and dry the water off the vial.

According to the conditions: g>f sink g has something to say on qq: 1219056654

(1) Fill the graduated cylinder with an appropriate amount of water, and measure the volume as V1. Then take a flat-bottomed test tube filled with a small amount of sand and measure the mass m1. The tube is then placed into a graduated cylinder with water to float and the volume is v2.

Finally, change the mass of the loaded sand and make several measurements as described above.

2) The volume of water v1 of the tube and the mass of sand m1 of the volume of water after being placed in the tube v2

Collect fruits** almost.

(1) Fill the graduated cylinder with an appropriate amount of water, and measure the volume as V1. Then take a flat-bottomed test tube filled with a small amount of sand and measure the mass m1. The tube is then placed into a graduated cylinder with water to float and the volume is v2.

Finally, change the mass of the loaded sand and make several measurements as described above.

2) The volume of water v1 of the tube and the mass of sand m1 of the volume of water after being placed in the tube v2

Sample, don't understand to ask the teacher.

It's strange, I also graduated from junior high school, why don't I know how to write.

You can set the standard steps in the textbook.

The idea is: measure the side length a of the cube, hook the metal block with the dynamometer and put it into the sink, and record the data according to the depth b1 and (gravity minus the dynamometer reading at the moment) according to the depth b1 and (gravity minus the dynamometer reading at the moment). It is important to note here that the metal block should not be completely submerged in the water.

The formula used for nuclear nuclear arrest is f=kx, p=f s, s=a 2

A = (m2- m1) (v2- v1) = 1g cm3 Table 1 data for the first time.

M A = - A v1 = 10g

Beaker mass M cup = M1-M A = 20g

The third question: the candle can be placed at a distance, usually about 10 times the focal length (the focal length for the experiment is about 5cm 30cm), so that it is about 3m, aim at the candle with a convex lens, put the light screen behind the lens, and move back and forth until the light screen becomes a clear image, at this time the distance from the convex lens to the light screen is equal to the focal length.

Principle: When you are much larger than the focal length, v f

Aim the candle with a convex lens, place a light screen behind the lens, and move it back and forth until the light screen forms a clear inverted image of the same size, at this time the distance from the convex lens to the light screen is equal to twice the focal length.

(3) Can be analyzed: can a match be used as a light source to measure the focal length of a convex lens?

The principle is that the wine bottle filled with water is like a convex lens, and when the object distance is less than the focal length, the convex lens becomes an upright magnified virtual image.