Physics, add 10 points if you answer well, and add 10 points to a physics question

Galileo really didn't do this experiment.

Galileo only said that if there were two stones, one large and one small, falling from the top of the tower together, then according to the experience of the people of that time, it must have been the heavier (i.e., the big stone) that landed first. So if you tie these two stones together and let them fall, as a rule of thumb, if two stones are heavier than one stone, they're going to fall faster, but the other way around: the big stones are going to fall faster than the small stones, and if they are tied together, they're going to fall slower because of the small stones.

In this way, according to the experience of the predecessors [the heavier physical fall is faster], the falling speed of the two stones is different. So it turns out that [the heavier physical falls faster] is a paradox.

But he really didn't do the experiment.

It's not that the principle is wrong, it's that the principle is that under vacuum conditions, air resistance is ignored.

There should be a story in the language book about two iron balls landing at the same time, which is the Leaning Tower experiment. Galileo released two iron balls of different masses at the same time at the Leaning Tower, resulting in both iron balls falling to the ground at the same time. This was a big departure from people's understanding of mechanics at that time, so it caused a sensation.

At that time, people's view was that force was the reason for maintaining the motion of objects, for example, if you pushed a cart, the cart would stop when you didn't push it, and in line with the theory of the time, if you pushed the cart with more force, the cart would run faster, so people thought that the ball with the most mass should be hit first by the gravitational force. But Galileo's experiments just proved their theory wrong.

Both balls have a gravitational force much greater than the air resistance they experience during their fall, so they hit the ground at the same time. However, the gravitational force is slightly greater than the air resistance during the fall, so the influence of air resistance cannot be ignored, and the falling speed will be less than that of the iron ball.

Galileo Galilei once did such an experiment: he climbed to the top of the Leaning Tower of Pisa and dropped two iron balls with very different weights at the same time, and observed that both iron balls fell to the ground at the same time, thus disproving Aristotle's theory that "the speed of falling of an object is proportional to its weight".

There is no problem with the principle, at least not for now. In his experiments, the effect of air resistance was not particularly large, that is, Galileo did not take into account the effect of air resistance. Now you experiment with a piece of paper and a stone, and the air resistance has a great effect on the paper, and it is much smaller for the stone, and the premise of your experiment is problematic.

Galileo's Leaning Tower experiment was to drop two iron balls of different sizes from the same height of the Leaning Tower at the same time, and the result was that both balls hit the ground at the same time.

A piece of paper and a stone are thrown from the same height at the same time but do not land at the same time, not because of the wrong principle. Instead, the resistance of the air on the paper is greater and the resistance of the air on the stone is greater, so the downward acceleration of the paper is less than the downward acceleration of the stone, so the time for the paper to reach the ground is longer than the time for the stone to reach the ground.

This experiment is about a free-fall motion in which iron balls of different masses are thrown from the same height at the same time, and the iron balls fall to the ground at the same time. The reason why you did the wrong experiment is because the air resistance of paper and stone is different, if you want to do this experiment, you can find two iron balls and plastic balls of similar volume.

Galileo's Leaning Tower experiment was in which a heavy iron ball and a light iron ball were lowered from the leaning tower at the same time without initial velocity, and both iron balls fell at the same time (the two iron balls were of the same density and experienced almost the same resistance).

Because there is a resistance in the air, this resistance is not the same for stone and paper.

The Leaning Tower experiment is that two iron balls are thrown down at the same time, and the air resistance is quite the same, almost the same, and the air resistance of a piece of paper and the stone is different, so it will not hit the ground at the same time.

It's a matter of air resistance, and the theory is correct.

He lowered a 10-pound iron ball and a 30-pound iron ball from the leaning tower at the same time, both landing on the ground.

Legend has it that it was at the Leaning Tower of Pisa.

But it was denied by ruthless historical research.

Because scholars at the time generally believed that the speed of an object in free fall was related to mass, and Galileo believed that it was not, he let two heavy balls with different masses fall from the tower at the same time, and the result was almost the same landing, proving that it was not related to mass

A piece of paper and a stone thrown from the same height at the same time can land at the same time in a vacuum, but there is air resistance in actual operation, and the effect of resistance will be obvious for small and light objects such as paper.

Regardless of air resistance, it should land at the same time.

When there is air resistance, the resistance of an object of the same size is about the same, while the gravitational force of a denser force is much greater.

So there is. g large - f) m large > g small - f) m small.

This principle is correct, because you don't consider the buoyancy of air, the success of the iron ball experiment is first because the iron ball is heavier, and the influence of buoyancy can be basically ignored, and secondly, the volume of the two iron balls is the same, so the buoyancy is also the same.

You can try revalidating this experiment with a piece of chalk and a pen

The paper is too light and the resistance to the air is too great.

The principle is correct.

Experiment with something high in density.

Table 1: Number of experiments l 2 3 4 5

The current is represented by the number a

The voltage represents the number v 0

Resistance r=u i 0 5 10 15 20

Power p ui w 0

Number of experiments 1 2 3 4 5

The current is represented by the number a

The voltage is represented by the number V 8

Resistance r = u i 48 41 30 26 20

Power p ui w

From the above calculations, it can be seen that:

When the resistance r of the sliding rheostat is 20, the power dissipated by the sliding rheostat increases with the increase of the resistance of the sliding varistor.

When the sliding rheostat resistor is 20, the power dissipated by the sliding rheostat decreases as the resistance of the sliding rheostat increases

R0 and the sliding rheostat are connected in series, so the power of the sliding rheostat is [U (R0 +R)] 2*R

That's right, when r < r0, the power consumption of the sliding rheostat increases as the resistance of the sliding rheostat increases.

When r > r0, the power consumption of the sliding rheostat decreases as the resistance of the sliding rheostat increases, and you can calculate it with the above data.

Voltage and current have both ends of the resistance u r i r power u r * i r can be listed in a table to see more than 20 and less than 20.

If you can't learn in this way, you can ask your classmates or teachers if you don't know the questions, and it will be more effective to learn in reality. Don't do questions for the sake of doing questions, doing questions is to check and fill in the gaps, to see what knowledge has not been mastered, so that you can improve.

1) If the radius of the wheel is x, then 18x=

x = so linear velocity = m s

2) When the left end of the board is half the length of the O10 plank, the board will flip.

So the horizontal distance of the plank is , and the translation time is 16 r seconds.

3) The friction force f=20*10*, and the moving distance is. Multiply.

The mechanical energy consumed.

Solution: 1) 2r=

r=v=2 rn (n is the rotational speed).

2) When the plank is half on the wheel and half in the air, it is the critical point, so the total displacement of its motion is s=.

The acceleration of the motion of the plank a= g=

Then judge whether the plank falls after reaching the maximum speed, or if it does not reach it, it falls, using the following formula.

vt squared = 2as

If , then vt=at

If , then accelerate first, then at a constant speed.

3) The mechanical energy consumed is equal to the kinetic energy gained by the plank.

There should be a ** in this question, you can take a picture of it and let me see it.

(1) Do your own math.

2) Molecules move in a random and irregular way that never stops. (3) Yes.

1) Ink diffusion opens molecular movement.

2) Yes.

Xiao Ke observed that his electric water heater has high, medium and low three gears, he consulted the manual and found his electrical schematic diagram as shown in the figure below, which has two touch switches S1 and S2, where the resistance value of R1 is, when R2 is connected to the home circuit alone and works normally, its electric power is 1200W

1) When S1 is closed only, it is in the (low) temperature range, and its power is (800) W

2) How long does it take to heat 80 l of water in the tank from 20 to 70 when this electric water heater is working in high gear (the efficiency of the water heater is 84%)?

q=m=1000kg/m^3*

t=cm(t2-t1) (seconds=hours.)

3) (A) in A and B is the hot water outlet, and the reason why the F pipe is designed to be higher than the E pipe is (the hot water density is small and located above the water heater).

1. The camera, into an inverted and scaled down real image.

2. Use a camera with a large focal length to capture the image of the scene, (because the focal length is large, the imaging appears very close, and the near image of the object becomes larger, so the image of the scene photographed is larger).

1.The objective lens of the telescope is equivalent to the lens of a magnifying glass, and the object is imaged by the objective lens to obtain a magnified and upright virtual image.

2.If two cameras with different focal lengths are used to capture the same scene at the same location, the image size of the scene is captured with a camera with a large focal length.

3.Use a projector to project the "E" on the film, just forming a clear image on the screen, keep the projector away from the screen and put the lens down.

Known length, diameter is, p steel = cubic kg m

Find out how many kilograms of this steel you need at least.

Untie. Volume v=(

Mass m = pv

A: At least this kind of steel.

The known mass is that the total mass when filled with water is and the total mass when filled with a liquid is.

Water density p=1000kg m3

Find out what is the volume of this container.

What is the density of the liquid.

How many grams of mercury can be held in this container.

Untie. v=mwater, pwater=

p liquid = m liquid v = cubic 1000kg m 3 A...

It is known that to prepare 100 ml of saline = that the density of the saline is cubic kgm

Seeking: How many grams of salt do you need?

Untie. m=pv=cubic kg m * A.

It is known that the mass of the empty bottle is m, the mass after filling with water is m1, the mass after filling with oil is m2, and the density of water is p1

Find out what is the density of oil p2.

Untie. m water = m1-m

v=mwater p1=(m1-m) p1

M oil = m2-m

P2=M Oil V=(M2-M)*P1 (M1-M)A.

It is known: the mass of alloy crafts made of gold and copper is 40kg, the volume is cubic decimeters.

How many kilograms of gold and copper are in this handicraft?

Establish. Gold and copper are given for. xy

kgx+y=40

x p gold + y p copper = A...

Known: Two solid square blocks of wood, the sides of the large block are twice as long as the sides of the small blocks.

Find: the ratio of their volumes.

Mass ratio. Density ratio.

Solution: The side-length ratio is 2:1

The volume of the body = the cubic length of the side.

The volume ratio is 8:1

Mass = Volume * Density.

Mass ratio = volume ratio = 8:1

Density ratio 1:1 A...

It is known that the density of the glass ball is the cubic kg m and the density of the iron ball is the cubic of the mountain and the masses of the two balls are equal.

What is the ratio of the volume of a glass ball to an iron ball?

Untie. The density ratio is.

The mass ratio is 1:1

Volume = mass density.

Volume ratio 78:25

Answer... 8.The mass of the two ores of A and B is equal, and the volume of A is twice that of B, if A is cut off by one-third and B by two-thirds, then the relationship between the density of the remaining two ores is p A = p B?

9.Three identical beakers contain water, and when the aluminum, iron, and copper blocks of the same mass are put into the three cups of water, the liquid level of the three cups of water is just equal, and the cup holds the least amount of water.

10.In three identical bottles, each containing the same quality of water, alcohol and sulphuric acid, the highest level is the bottle, and the lowest level is the bottle.

Know, seek, solve, answer, know, seek, solve, answer, know, seek, solve, answer, know, seek, solve, answer

Set hot water x kg.

Q Suck = Q Release.

cm1△t1=cm2△t2

x（95-45）=（9-x）(45-20)∴x=3

3 kg of hot water and 6 kg of cold water.

1.According to the problem, the force experienced by the iron ball is divided into gravity (downward), buoyancy (upward), tensile force (along the inclined plane), and support force (vertical inclined plane).

Where the direction of gravity and buoyancy is opposite, by the density relation, the buoyancy = gravity

Buoyancy: Gravity = Water Density * Volume: Iron Density * Volume = Water Density: Iron Density = 1:

That is, the downward force applied to the object at this time is: gravity - buoyancy = gravity

Since the process of this tensile force is a uniform acceleration process, the resultant force of the inclined plane support force and the tensile force is exactly equal to the downward force experienced by the object. Drawing a triangle with a force synthesis has:

f tensile force = f combined sina, (a is the angle of inclination of the inclined plane).

According to the question, the length of the inclined plane is, height, i.e. sina=

i.e. f together = f pull*

By: gravity - buoyancy = f = gravity

So: gravity = 79 (n).

2.The key to this is to know the weight of B, and then to get the work done by f according to the work done by external force = change in mechanical energy.

There is a question: m A: m B = s A * h A * A density: s B * h B * B density.

And since the pressure is generated by the gravitational force of A and B, there are:

p = (g A + g B) s A = 5g B s A (the contact surface is the bottom surface of A).

g B = p * s A 5 = 7500 * (20 10000) 5 = 3 (n).

Then the work done by f: w=g, bh=3*1=3(j).

Since it is moving at a uniform velocity under the action of f, its kinetic energy does not change, and the change in mechanical energy is equal to the change in gravitational potential energy at this time).