A physics problem, I beg everyone to hurry up, I m going to hand it in tomorrow

The filament (tungsten filament) is sublimated into tungsten vapor by heat, which condenses when it encounters the cold bulb wall, forming black particles.

In winter, water vapor meets cold windows and condenses, forming ice flowers.

In winter, the water vapor in the air condenses into solid frost.

The actual phenomena of condensation are: on winter nights, indoor water vapor often condenses into ice crystals on the window pane; "rime" on tree branches, etc.; The electric bulb will appear black after a long time, because the tungsten vapor formed by the heating and sublimation of the tungsten filament condenses on the wall of the light bubble into a very thin layer of solid tungsten. Another example is the formation of "frost" in nature.

Condensation, for example, the formation of frost.

The formation of frost is related not only to the weather conditions of the time, but also to the properties of the object to which it is attached. When the temperature of the surface of the object is very low, and the air temperature near the surface of the object is relatively high, then there is a temperature difference between the air and the surface of the object, if the temperature difference between the surface of the object and the air is mainly caused by the radiative cooling of the surface of the object, then the air will cool when the warmer air and the colder surface of the object come into contact, and the excess water vapor will precipitate when the water vapor is supersaturated. If the temperature is below 0°C, the excess water vapor condenses into ice crystals on the surface of the object, which is called frost.

Condensation: The phenomenon that a substance changes from a gaseous state to a solid state without going through a liquid state.

On winter nights, the water vapor in the room often condenses into ice crystals on the window pane and gathers into ice flowers; The flask with iodine vapor is cooled and dissipated, and the iodine vapor will be directly condensed into solid iodine; The electric bulb will appear black after a long time, because the tungsten vapor formed by the heating and sublimation of the tungsten filament condenses on the wall of the light bubble into a very thin layer of solid tungsten.

Frost, frost is the process of condensation in which gaseous water vapor directly turns into a solid state.

1) Density of handicrafts: 600 52=

2) If the content is 50% each, then the volume of the Zen Chi handicraft is: v=300

3) The actual gold content can be calculated as follows: set to x, then Youchun is 600x, and the attack resistance equation can be solved.

Light a candle and see the candlelight with a piece of cardboard (can't).

Make a small hole in the cardboard (can't) [can't] see the candlelight.

Question] why not everyone can see the candlelight after opening a small hole (because different people have different distances to the real image formed by the small hole).

Think] How does light propagate through this phenomenon? Think] How does light propagate?

Solution] Equipment: laser pointer; Sprays.

Steps: Use a spray to create smoke and turn on the flashlight to let light pass through the smoke.

Phenomenon: The path of the light seen in the smoke is straight.

Conclusion: Light travels in a straight line.

Come on!

No. Yes.

Small hole imaging experiments because light travels in a straight line.

Light travels in a straight line.

No, the distance is different for each person Straight line Equipment and principle required for small hole imaging experiments Light travels in a straight line.

Solution: When pulled down in the direction of the inclined plane, the spring elongation is minimal, and there is:

k△l1+mgsinθ=f1

When pulling upwards in the direction of the inclined plane, the maximum elongation of the spring should be made, and the maximum static friction force at this time can only be equal to f1 (the movement of the wooden block is exceeded).

k△l2-mgsinθ=f1

Lian Li solved.

The maximum static friction f1 = ( l2 + l1) * k 2 is different from the answer above, who is right and who is wrong, I am a little confused, you judge for yourself, it is best to ask the teacher, there must be a mistake, and it is easy to make mistakes).

Let the maximum static friction force on the inclined plane of the wooden block be x, then the spring elongation is the smallest when x is up along the inclined plane, and the maximum spring elongation when x is downward along the inclined plane.

k* l1+x=k* l2-x=the component of gravity downwards along the inclined plane.

x=(△l2-△l1)*k/2

En is x=( l2- l1)*k 2.

Let the maximum static friction force be f, the first direction f is along the inclined plane, let the spring tension force be f1, then f+f1=g*sin, the second f direction along the inclined plane, let the spring tension be f2, then f2=g*sin +f, and the result can be obtained by substitution.

The energy consumed by the two frictions is the same, q=1 2mv 2-1 2m(1 2v) 2, and in the second time, 1 2mv 2-q=1 2(m m)v 2, mv=(m m)v. m m = 3

The common denominator of the two modes of motion before and after is that the heat energy consumed by the bullet in the motion of the wooden block is the same (q=1 2mv 2-1 2m(1 2v) 2), so there is the kinetic energy equation of the second motion: 1 2mv 2-q=1 2(m+m)v 2 where the above equation can be obtained by the conservation of momentum mv=(m+m)v to solve the above equation.

Downstairs is correct and admits mistakes.

The heat energy consumed twice is the same, and if the velocity of the second uniform motion is a, mv 2-m(v 2) 2=mv 2-(m+m)a 2mv=(m+m)a

Substituting a mv (m+m) into the equation yields.

m/(m+m)=1/4

So, m m = 3

So, the ratio of the mass m of the block to the mass of the bullet m is 3

The heat energy consumed twice is the same, and if the velocity of the second uniform motion is x, mv 2-m(v 2) 2=mv 2-(m+m)x 2mv=(m+m)x

Substituting x mv (m+m) into the equation yields.

m/(m+m)=1/4

So, m m = 3

So, the ratio of the mass m of the block to the mass of the bullet m is 3

The decrease in the kinetic energy of the bullet is the sum of the increase in kinetic energy of the block and the energy expended by friction. The frictional energy consumed by both times is the same, both are q=δek=3 8mV2. So:

Q+1 2mv 2=1 2mv 2-1 2mv 2,(m+m)v=mv, where v is the common velocity, and m m=3 is solved

1) The buoyancy received by the iron ball is equal to the gravitational force of the water discharged by the iron ball.

Buoyancy = density of water g volume of iron balls.

2) The gravitational force experienced by the iron ball should be the volume of the actual iron fraction multiplied by the density of the iron.

Gravity g = iron ball density 4 5 iron ball volume.

3) The basis for judging the motion of the iron ball is the relationship between the two forces calculated in the previous two questions.

If the buoyancy of gravity floats up.

If buoyancy = gravity is suspended.

If the buoyancy of gravity sinks.

1, f = liquid density * volume of drained water (complete immersion is the complete volume of iron balls) * g = 10 (n).

2. Gravity is the force given to him by the earth, which has nothing to do with buoyancy, g = the volume of the iron ball (the actual volume, excluding the hollow part) * the density of the iron ball * g =

3 Because it is completely submerged at this time, the buoyancy reaches its maximum, and the gravity is greater than the buoyancy (>10), so it sinks.

1. Buoyancy = water density x gx volume = Newton.

2. Gravity = volume of iron (1 5 volume of hollow spheres) x railway density xg = Newton.

3. The average density of hollow iron balls: >1, so they will sink.