Ask a few physics questions in the second year of junior high school . Hurry, hurry!

The volume of the bottle = the volume of water.

v volume = v water = m water water = 1kg 1000kg m 3 = method : the mass of a full bottle of alcohol.

M wine = wine v capacity = 800kg <1kg, so it can't hold 1kg of alcohol.

Method: 1kg volume of alcohol.

V wine = m wine = 1kg 800kg m 3 = >v capacity, so it can't hold 1kg of alcohol.

The increased mass of the liquid corresponds to the increased volume of the liquid, and the density of the liquid is obtained by dividing it.

m2-m1)/(v2-v1)=(

The mass of the first liquid is calculated as.

M solution = V1 = 1 g cm3

M cup = M1-M liquid =

m1 is the mass of the first liquid and the mass of the measuring cup).

1.(1) Explain that the loudness of the sound is related to the amplitude.

2) The sound becomes smaller, and the loudness is also related to the distance.

2.The distance is transmitted out and reflected back, a total of twice, then the distance = 2 * 340 = 680 m s

3.Distance = Time * Speed = 2s * 340m s = 680m s

Categories: Education Academic Exams >> High School Entrance Examination.

Problem description: Blindfold your friend and make him sit quietly in the room** without turning his head. Then, you take two coins and strike them directly in front of him or directly behind or directly above him, as shown in Figure 1-2-1Now ask him to tell him where to knock the coin, and he will surprise you.

For example, when the sound book takes place in the corner of the room, he points to the exact opposite corner. Give it a try and discuss what the reasons for this phenomenon are.

When there is a loud noise around people, it is easy to damage the eardrum and cause hearing problems, what effective methods can you take to avoid causing damage?

Gently bite the top end of the pencil with your teeth and tap the bottom end of the pencil with your fingers (Figure 1-2-2) and listen for the tapping sound. Then open your mouth so that your teeth don't touch the pencil. The position of the pencil remains the same, and the finger taps the lower end of the pencil with the same force as before.

Compare the percussions heard these two times. What this experiment can say?

Thank you, I'm in a hurry!

Analysis: 1This is due to the reflection of sound, and it is better to give the diagram you are talking about.

2.Plug your ears with your hands and open your mouth.

3.The sound is different from the two times, and the sound heard by biting the pencil is stronger, because the sound of biting is transmitted directly to the ear through the pencil, teeth, and bone spines, and the attenuation is reduced. Do not bite the sound through the air propagation attenuation is large.

This phenomenon shows that solids can propagate sound.

Total resistance in the circuit: r = u i = 3 (30 10 -3) = 100

The resistance of the power supply is not counted, nor is the resistance at the short circuit, and the total resistance is equal to the resistance of the two sections of the transmission line.

The distance between the short circuit and ground A: x = (100 = 5000m.)

5000 meters.

The total resistance is 100, and if the two wires are connected in series after a short circuit, the resistance of each wire is 50...

1) Use a scale to measure the distance of walking 10 steps in a straight line with a scale, and divide by 10 to get the step distance;

2) The length of the teaching building is: s=, and his walking speed is: v=st42m35s

Answer: The speed of his step and line is;

3) The height of the raised center of gravity h=65cm-

Root number (65 2 25 2

cm=5cm=；

w=gh=mgh=50kg×10n/kg×；

Answer; The work he does to overcome gravity is 25 J for each step;

The mass of the object does not change with the change of the state of the object, so m water = m ice.

M Ice = P Ice V Ice =

m water = m ice = 72 g

v water = m water p water = 72g 1g cm 3 = 72cm 3v water'= m water p water = 2100g 1g cm 3 = 2100cm 3rd floor master oh!

The mass of water can be calculated according to the equal mass, and the volume of water can be calculated according to the formula: mass = density * volume.

m ice = m water.

v ice * ice = m water.

80cm* water.

m water = 72 g

v water = m water water = 72g (1g cm) = 72cm m'Ice = m'Water.

Water* Water. v'Water =

v'Water = 2100cm