Junior 3 Physics Lever Theorem, Junior Physics Lever Principle

The concentrated sulfuric acid, which has the same volume and concentration, is also of equal mass, so the mass in the cup is equal.

The inner diameter of the cup is the same, which tells you that the area of concentrated sulfuric acid in contact with the air is equal, and the rate of absorption of moisture in the air is also the same.

The lever is unequal to the arm, and it is balanced, the arm A is short, and the arm B is long, so the mass of cup A is lighter than cup B, which is the meaning of the difference in wall thickness between the two cups in the title.

At this point, the basic analysis of the conditions in the problem is complete, and the lever is balanced, but not equal. The concentrated sulfuric acid in the two cups should absorb water at the same rate, which is equivalent to adding the same quality of water to the two cups at the same time. Choose the second answer.

The problem is actually a trick to get rid of all the mess, that is, what happens if you put the same mass on a lever with unequal arms, and you will definitely do it.

Hope it helps.

The answer is: B analysis: now the leverage is balanced, indicating the left and right, according to the principle of leverage, it can be known:

The glass on the left is the one with a thicker wall. That is, the mass is slightly larger than the one on the right. Because their inner diameter is the same, the surface area of concentrated sulfuric acid in contact with the air is the same, that is, they absorb the same amount of water in the air.

After a while, the weight gained on both sides is the same. In this case, the force distance on the right side is long, so the right side will press the left side up.

Phenomenon: The leverage on the A side rises.

The concentrated sulfuric acid is the same, so the weight gain mass after a certain period of time is also the same that intuitively. b set the original mass as ma mb and increase the weight m

ma*ao=mb*bo

After a while (ma+m)*ao (mb+m) (because ao bo) is going down to the right.

The left side came up.

Select: B. It should be "it contains concentrated sulfuric acid of the same volume and concentration", indicating that the absorbed water is the same, and the B-terminal force arm is long. So, the A-side goes up.

The A-end is rising!!

The sulfuric acid in the two cups is the same, and the weight increase of concentrated sulfuric acid after water absorption is also the same. However, the moment on the right side is long, so the right side (b) drops first with the same weight.

First analyze which side has more water Force 1 Force Arm 1 = Force 2 Force Arm 2 Concentrated sulfuric acid has water absorption AB absorbs the same water at both ends B end will decline Reason Force 1 Force Arm 1 Force 2 Force Arm 2 Therefore, choose B

A starts with the same moment on both sides Moment = force multiplied by force arm Sulfuric acid absorbs water The force on both sides increases the same amount but b is longer than a arm then the moment increases more b decreases a rises.

b, when the resistance arm is greater than the balance of the power arm, the volume increases, and the same mass increases, the bar will rise to the A end.

The A end rises because B is farther away from the fulcrum.

b Add the same weight at both ends, and A will rise.

I should choose D.,I didn't tell which one was thick.。

A hard rod that can rotate around a fixed point under the action of force is called a carrying rod.

Fulcrum: The point around which the lever turns.

Power: The force that makes a lever turn.

Resistance: The force that prevents the lever from turning.

Power arm: from the fulcrum to the power line.

Resistance arm: From the fulcrum to the resistance action line.

There are three types of poles:

1. Labor-saving carrying rod, the power is less than the main force, and the power arm is greater than the resistance arm. Such as crowbars, paper cutters, wire cutters, etc.

2. Laborious to carry the rod, the power is greater than the resistance, and the power arm is smaller than the resistance arm. Such as food tongs, tweezers, etc.

3rd class arm carrying bar, power is equal to resistance, power arm is equal to resistance arm. Such as pallet balances, seesaws, etc.

The conditions for the equilibrium state of the pole are:

1 Power * Power Arm = Resistance * Resistance Arm.

It is expressed as f in an algebraic formula

l1=w•l2。where F represents the power, L1 represents the power arm, W represents the resistance, and L2 represents the resistance arm.

2. The carrying rod is stationary or moves at a constant speed around the fulcrum.

The lever on the lid of the barrel is a laborious lever, and if the force acting on BC is f1, there is f1·o2c=g·o2d, which is substituted.

f1 = g·o2d o2c = mg·o2d o2c = for pedals.

Let the force of the pedal be f2, f2·o1a=f1·o1b

So f2 = f1 · (o1b o1a) = 35 (

According to the Pythagorean theorem, AD=100cm. From the lever equilibrium condition, it can be seen that f ad=g de, f=(de ad) g=(30cm 100cm) 2200n=660n

To save effort, it is necessary to have a long arm.

The longest arm of this oil drum must be the line of BC.

Then the direction of the force is obtained by decomposing the gravity of the oil drum along the perpendicular line of the BC line at point B by trigonometric formula.

This force f=2200*30 100=660n

I'm here to help you, a good student who loves to learn.

Solution: According to the lever equilibrium condition, f1 l1 = g object is 8n solution, and the gravity of the object g = 12n

Because the gravity of the ball g=mg=, let's say: when the minimum distance of the ball is l, the tension of the string is zero, (that is, the ball and the weight balance the lever horizontally, if the rope is cut with scissors, it has no effect on the lever).

Therefore, the g ball l=g matter i.e. 5n l = 12n solution l=, the ball moves at least for t=s v=

I appreciate your love to fundamentally understand the problem and learn attitude, the confusion has been explained in parentheses, I wish you continuous progress!

This one is easy, the gravity of the weight g is 12n, and the gravity of the ball is. When the ball moves to a distance of x meters from point O, the gravity of the ball and the gravity of the weight g form a lever balance for point O (the rope no longer works).

5*x=g*

Get: x = g * m = 96 cm.

When the fulcrum is 30cm away from the thick end, the wooden stick can maintain horizontal balance, the meaning of this sentence is that the center of gravity of the wooden stick is 30cm away from the thick end, when the fulcrum moves to the position of 50cm, it is equivalent to the object hung at the distance from the fulcrum (50-30) = 20cm, at this time the thin end of the wooden stick is away from the fulcrum (90-50) = 40cm, according to the principle of the lever, let the weight of the object that needs to be hung g, then.

40g=, get g=.

(50-30)* Objects hung at the end of the thin end to bring the lever back to horizontal equilibrium.

A and C If the rescue team members pry up the stone in the direction of DM at point D of the crowbar, then the crowbar is also affected by the pressure of point B on it, so that the lever rotates around point A, so A is the fulcrum. If the rescue team member pries up the stone 1 along the DN direction at the point D of the crowbar, the crowbar is also subjected to the pressure of point B on it, so that the lever rotates around point C, so C is the fulcrum.

a /c

The idea is that the point that does not move is the knock point, and when you see the lever moving, which point does not move is it.

And the crowbar, which is straight. This topic is really not good, hehe.

(2) using a crowbar, the rescue team member pries up the stone that rolls down on the road, as shown in the figure, if the rescue team member pries up the stone along the DM direction at the point D of the crowbar, the fulcrum of the crowbar is point A; If the rescue team member pries up the stone 1 in the direction of DN at point D of the crowbar, the fulcrum of the crowbar is point C

Because the line of action of the force indicates that the force arm of the force is 0 through the fulcrum, that is, this force has no effect on the state of the lever.

The words of c are not necessarily fulcrums.

As long as the reverse extension of the force passes through the fulcrum, it is fine.

For example, the one below is a thick uniform lever o as the fulcrum.

for the force. This force also has no effect on the state of the lever.

So C is wrong.

o －＝f

1、 o

f1l1l2f2

Five elements - a schematic diagram of the composition lever.

Fulcrum: The point at which the lever turns. It is denoted by the letter o.

Power: The force that makes a lever turn. It is denoted by the letter f1.

Resistance: The force that prevents the lever from turning. It is denoted by the letter f2.

Description Both power and resistance are the forces of the lever, so the point of action is on the lever.

The direction of the momentum, the resistance is not necessarily the opposite, but they make the direction of the rotation of the lever in the opposite direction of1l1

L2F2 power arm: the distance from the fulcrum to the line of action. It is denoted by the letter L1.

Resistance arm: The distance from the fulcrum to the line of action of resistance. It is denoted by the letter L2.

Draw the force arm method: one to find the fulcrum, two to draw the line, three distances, four labels to find the fulcrum o; draw the action line of the force (dashed line); Draw the force arm (dashed line, the line of action of the vertical force through the fulcrum is the perpendicular line); Standard force arm (braces).

Five elements - a schematic diagram of the composition lever.

Fulcrum: The point at which the lever turns. It is denoted by the letter o.

Power: The force that makes a lever turn. It is denoted by the letter f1.

Resistance: The force that prevents the lever from turning. It is denoted by the letter f2.

Description Both power and resistance are the forces of the lever, so the point of action is on the lever. Sometimes the setting of power and resistance is not absolute, and can be set freely. The force exerted by an average person is set as the driving force.

The direction of the motive force, the resistance is not necessarily reversed, they make the direction of the rotation of the lever in the opposite direction Power arm: the distance from the fulcrum to the line of action of the motive force. It is denoted by the letter L1.

Resistance arm: The distance from the fulcrum to the line of action of resistance. It is denoted by the letter L2.

The drawing arm is the distance from the point to the straight line.

Draw the force arm method: one to find the fulcrum, two to draw the line, three distances, four labels to find the fulcrum o; draw the action line of the force (dashed line); Draw the force arm (dashed line, the line of action of the vertical force through the fulcrum is the perpendicular line); Standard force arm (braces).

Use your arms as an example: hold a glass of water in your hand, use your elbow joint as a fulcrum, and your hand and arm do not move, and you lift the glass upward.

The water cup presses down on your hand due to its own weight, that is, the hand is subjected to vertical downward resistance f2 and the muscles in the middle of the forearm stretch to drive the whole, and the upward force of the arm is the power f1 Basically, the power is the force that the person wants to exert, and the resistance is the force that hinders you from carrying out this act. You can feel it with a cap driver and a claw hammer.

Draw the resistance and power direction on both sides of the fulcrum, and the opposite force arm in the direction of the same side is the distance from the action line of power and resistance to the fulcrum, and draw the vertical line segment.

Grab f1l2=f2l2 and the five elements ==[[Anyway, we have to spank the ass ==

Find a good fulcrum, power arm and resistance arm can be.