The sooner the better

Observing the flashlight, the students first unscrewed the back cover to observe: how is the battery placed? Before the positive electrode and after the negative electrode.

How is the back cover connected to the battery? The negative pole of the battery is connected to the back cover.

What is the function of the spring on the back cover? 1. Wire; 2. Squeeze the battery so that the positive and negative electrodes of the battery are in good contact;

Try to push the metal slider forward, the metal slider is connected to the light bulb? The metal slider is connected to the metal housing, and when the metal slider is connected to the positive press sheet, the bulb emits light.

When the metal slider is pushed forward partially, press the button, and the slider is also connected to the positive terminal of the battery, and the bulb glows. Unscrew the front to see how the bulb is connected? The tin block at the tail of the bulb is connected to the positive electrode of the battery, and the other metal parts are connected to the metal housing (negative electrode).

Why is there a piece at the tail of the bulb? What does it do? The role of the tin block is to act as a wire, connecting the positive pole of the battery and the filament.

The battery is, of course, mounted in this way from positive to negative. Springs are also part of the circuit that act as both conductors and are designed to prevent loosening. Slide the metal slider and the light will have a noticeable change in brightness and darkness.

Both the bulb and the metal slider are connected in series. The role of the tin block, this is not very clear, it seems that there is not.

The battery is connected in series, the back cover and the battery are also connected in series, the spring is to make the battery close contact, and the bulb does not emit light. The tin block at the tail of the bulb is electrically conductive.

It should be the connector of the wire, how can the filament be bright if it is not connected.

The answer is A. The same electric heater heats for the same time, which means that A and B absorb the same amount of heat q; The mass of A and B is equal, but the temperature of A increases by 20, and the temperature of B increases by 40, using the formula of specific heat capacity: Q=CM(T2-T1), it can be seen that the ratio of specific heat capacity of A and B is 2:

1, so A is right, B and C are wrong.

A and B raise the same temperature, using the above formula, it can be seen that the specific heat capacity of A is larger, so A absorbs more heat, and D is wrong.

To learn physics, you must master the basic formulas and theorems, and use the formulas to analyze them.

Analysis: The same electric heater works for the same time and emits the same amount of heat, i.e., the two liquids absorb the same amount of heat. When the mass of both liquids is the same, and the heating time is t, it indicates that both liquids absorb the same heat, so C is wrong.

The ratio of their specific heat capacity is:

C1: C2Q M(T1 T0): Q M(T2 T0) So A is correct.

In answer D, AB increases by the same temperature, because the specific heat capacity of A is larger, therefore, A absorbs more heat. d error.

Because the heating time is the same, and then the heat released by the fuel is also the same, indicating that the two substances of different ab absorb the same heat, but the temperature of one of the increases is twice the temperature of the other, which can only mean that its specific heat capacity is 1 2 of the specific heat capacity of the other object, so the correct answer should be the answer a, absorbing the same heat, the higher the temperature rise, the smaller the specific heat capacity, and the lower the temperature rise, the greater the specific heat capacity.

Choose a for this question, the same electric heater, heating the same time, the temperature of b rises from 20 to 60 degrees, an increase of 40 degrees, the temperature of a rises from 20 degrees to 40 degrees, an increase of 20 degrees, the smaller the temperature change, the greater the specific heat capacity, the smaller the temperature change of a, so the heat capacity of a is larger, 20 40 = so the heat capacity ratio of a and a is 2 1

No. No, the direction of life will change because of your thoughts, sometimes choice is a very important thing, if you find that this direction is wrong, change it, but if you change it and find that it is still wrong, you should think about whether the original choice is not wrong, the wrong thing is that you did not insist, there is not enough time to judge whether this direction is right or wrong. The choice of the direction of life is not.

If A is selected and heated for the same time, the temperature raised by A is half that of B, indicating that the endothermic capacity of A is twice that of B.

Far a, everything else can be pushed out is wrong.

1. Not true. His distance from the center of the circle does not change, but his position relative to the center of the circle is constantly changing. The displacement represents the change in the position of an object (particle).

It is a directed segment from the beginning to the end of the position, and its size is independent of the path, and the direction is from the beginning to the end point. It is a physical quantity with magnitude and direction, i.e., a vector.

2. The motion of two objects is relative. We only had to use the belt of the treadmill as a reference, and Grandpa ran 2km.

3. First flatten the ink bag of the fountain pen in order to press out the air inside, and then put the tap pen tip into the ink and let go. In this way, the ink is poured into the fountain pen under atmospheric pressure. This pen spills out on skydivers due to the decrease in atmospheric pressure at high altitude.

To overcome this difficulty, a ballpoint pen was created, which was open at both ends, and atmospheric pressure had no effect on it.

A person runs on a circular track. It has been said that; If you take the center of a circular runway as a reference. He's static, right, why.

Not to work out on the treadmill at home for Grandpa Xiaoping. Grandpa said I ran 2km. Xiaoping asked blankly, you have been there all along. How did you run 2km、What should grandpa say。

Let Xiaoping run and see what he has to say.

How do you hold ink in a fountain pen? This kind of pen will overflow on skydivers、Why、In order to overcome this dilemma Xiaoping Xiaoping created a ballpoint pen, how to solve this problem?

1.That's right, because the distance between the person and the center of the circle has not changed. 2.

Question 1:

Yes, when a person runs with the center of a circular track as a reference, the distance between the person and the center of the circle is always equal to the size of the radius, that is, there is no displacement. So he is stationary.

Question 2: Grandpa should say that the reference I chose was the belt that rotated on the treadmill, and I had a displacement of 2km relative to the belt that rotated.

Question 3: The body of a skydiver will overflow, due to the inertia of tap water, the object will always maintain its original state of motion, and when the athlete parachutes, the ink will overflow when it remains in its original state.

The exit of the ballpoint pen is sealed with a layer of wax, which inhibits the inertial action of the ink.

1. No, the direction has changed.

2. I let the track of the treadmill move for 2km

3. Use atmospheric pressure to load ink, high in the air, atmospheric pressure is less than the ground, ink overflow, beads are installed at the water end of the ballpoint pen, water can not overflow by itself, and the movement of beads is needed.

1.No, because his position relative to the center of the circle is also changing, so he is in motion.

2.Relative to the track movement took up 2km

3.The atmospheric pressure is used to load the ink, at high altitude, the atmospheric pressure is less than the ground, so the ink overflows, and the beads are installed at the water end of the ballpoint pen, and the water cannot overflow by itself, and the movement of the beads is required.

When pressing the pedal firmly to move the bike forward, the friction between the rear wheel and the ground is facing forward.

One way of thinking, when you press the pedal hard to make the bicycle move forward, the rear wheel has a backward force on the ground, and the force is reciprocal, so the friction between the rear wheel and the ground is forward.

Another way of thinking is that when you press the pedal hard to move the bicycle forward, the bike is subjected to a forward force, which comes from the friction of the ground against the rear wheel, so the friction between the rear wheel and the ground is facing forward.

The friction between the front wheels and the ground is rearward.

Former. You can observe for yourself the direction of rotation of the rear wheels. The rear wheels rotate backwards relative to the ground.

That is, there is a backward tendency with respect to the ground, and friction hinders this trend, so the direction is opposite, i.e. forward. Officially with this force, the car can move forward.

The front and rear wheels are just the opposite. Since the rear wheels are subjected to forward friction and make the car move forward, the front wheels are "pushed" forward, so that the relative ground has a forward movement tendency and will be subjected to backward friction.

The rear wheel rotates actively, and the front wheel rotates passively, so the rear wheel is also called the driving wheel, and the front wheel is called the driven wheel.

...... forward

Because when you pedal, the rear wheel has a tendency to turn backwards (although it does), and the friction prevents it from turning in the direction of forward, which makes the bike move forward. 、

Addendum: Since the rear wheel of the bicycle goes forward, the front wheel is forced forward and the friction force is backward (if the front wheel cannot be rotated, you can clearly see the scratches on the ground).

If you think about it yourself, you'll understand ......

Happy studying!

The friction between the rear wheel and the ground is facing forward, because the direction of rotation of the rear wheel is counterclockwise, relative to the ground is backward, so the friction direction is forward, and it is this friction that makes the bicycle move forward. The friction between the front wheel and the ground is backward, because the front wheel is the rear wheel that makes it move forward, it wants to hinder the forward movement, so the friction force is backward.

It must be the former !!

The relative movement of the rear wheels is backward, and the direction of friction is opposite, which is forward!!

The friction force of the wheels to the ground is backwards, so the force on the ground is forward, otherwise how can you move forward.

The part of the movement of the front and rear tires touching the ground tends to be backward, and the static friction he receives is forward.

At the same time, there is a small backward rolling friction.

I think it's forward, because the wheels are rolling backwards, and the friction must be in the opposite direction of the wheels, so it's forward, and if it's backwards, then your car will go backwards. The front wheels are the same because it is impossible for your wheels to turn one forward and one backward.

It is the tires of the car in front that turn backwards, so the friction is forward, so that your car can move forward

The friction of the rear wheels is forward, the friction of the front wheels is backward, and the friction of the rear wheels is greater than the friction of the front wheels.

1. w=fs=950n*

2.0j (no movement in the direction of force in 3 seconds).

3.0J (no force acting on the object), W=GH=1425J

1)w=gh=mgh=95kg*10n/kg*

2) 0 work is an accumulation of force to displacement. There is no displacement during the stay, so the work is 0

3) When the barbell is put down, it is generally allowed to fall freely, so the athlete does 0 work on it, and the work done by the gravity of the barbell itself and the work done by people on the barbell is an opposite process, so the two values are equal and 1425j

1.The time taken for the fuse to burn t=s v=96cm, 2The time it takes for a person to run to a safe zone 500m away'=s/v=500m÷5m/s=100s，3.So people can run to the safe zone before **.

OK. The time it takes for the fuse to burn is 96

The distance that an igniter can run during this time is 120 5=600m

So yes.

To run to a safe area 500 meters away from the ** location, it takes time 500 5 = 100 The fuse line burns at a speed of 96 cm long 96 120>100

She was able to run to a safe area 500 meters away from the location before **.

96 ,500 5 = 100, because 120>100, so you can reach a safe area.

Elementary school students, you have to read the book carefully.

This topic belongs to the problem of specific heat capacity in physics in the first volume of the ninth grade. There are two ways to change internal energy: heat transfer and work!

In this problem, when a hot lead block is placed in water at a lower temperature, heat transfer occurs, and when the temperature of the last two objects is the same, no heat transfer occurs, and part of the heat of the lead block is converted into water! The specific calculation is as follows:

The temperature after mixing is 18 degrees Celsius, and the temperature of lead and the temperature of water are the same when thermal equilibrium is reached, so the final temperature of lead is eighteen degrees Celsius.

Because lead is put into water, it will exchange heat with water, the heat release temperature of lead decreases, and the heat absorption temperature of water increases. As the heat exchange time increases, when the temperature of the lead finally drops to the same as the temperature of the water after it is heated, the temperature difference between the two is zero, and the heat exchange stops. The temperature at this time is called the mixing temperature.

So at this point the temperature of lead is equal to the temperature of water and the temperature of mixing is equal.

After the heat exchange of the closed system is completed, the whole system is a temperature, this problem should be seen according to the closed system, only the lead block and the water for heat exchange, the heat released by the lead block is equal to the heat that the water needs to absorb when it heats up;

specific heat capacity of liquid water;

200 * C lead * (98-18) = 80 * C water * (18-12) C lead = 80 * c water * 6 (200 * 80) =