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The car is driven by power, and the power is the friction force of the ground against the wheels (the driving wheels are generally the rear wheels). Just as when you swim, you paddle backwards and you move forward. However, when the car moves forward, it is also subject to drag (the frictional resistance of the ground from the power wheels, i.e., the front wheels, and the air resistance that increases the speed, the greater the resistance), and in order to overcome the influence of resistance, it is necessary to have the effect of power.

The principle is that the action of force is mutual, force is the reason for changing the state of motion of the object, and if it is moving at a uniform speed, there is also the knowledge of balanced force. There are no formulas available.

If the car is not subjected to friction, it will not move. On an infinitely smooth plane, the car moves in a straight line at a uniform speed, and it is not subject to friction and therefore does not require a force of equal magnitude to act on it.

However, on the road surface, the car is subjected to a frictional force in order to move forward. According to the two-force balance, it can be seen that in the process of uniform linear motion of the car, the forward friction force is received, and it will inevitably be balanced by a backward force, so the movement of the car requires the action of force.

The action of the force is mutual, the motorcycle has to act a force on the ground backwards, the ground will act on the motorcycle a forward force, the two forces are equal in magnitude, the direction is opposite, acting on different objects, the motorcycle moves forward, and the ground moves backwards. However, the mass of the earth is too large, and the amplitude of the movement of the ground is small and negligible.

You go to junior high school, if you go to high school, you're brain-dead.

According to Newton's third law, the friction is forward for the car and backward for the ground, and both are generated, changed and disappeared at the same time. According to the law of conservation of energy, the car will release heat to the environment (low-temperature heat storage) when it is in motion, and the heat will eventually be used in power. So.

If the wheels don't have force, there will be no friction and the car won't move forward.

The force is what changes the motion of the object, not what keeps the object in motion.

Summary. Hello dear<>

The answer you are looking for: an object with a mass of $m$ is moving in the positive direction of the $x$ axis with a velocity of $v 0$, and is subjected to a constant force of $f$ at an angle of $ theta$ to the direction of velocity. An object with a mass of $m$ falls freely from a height along an arc road with a radius of $r$ and an angle of $ alpha$ to the vertical direction, and the velocity of the object at the moment of leaving the road.

Thermal Problem: An ideal gas undergoes an adiabatic process with an initial state of $(p 1,v 1)$ and an end state of $(p 2,v 2)$, and the temperature change of the gas in this process is found. An object with a mass of $m$ hits a solid with a mass of $m$ and a temperature of $t$ with a velocity of $v 0$, and the object stops on the solid after the collision, and the amount of change in temperature of the solid is found.

Suppose the collision is a fully elastic collision with a heat capacity of $c$ and a thermal conductivity of $k$ of the solid, ignoring the volume change of the solid.

I'm going to ask physics questions.

Hello dear<>

The answer you are looking for: an object with a mass of $m$ is moving in the positive direction of the $x$ axis with a velocity of $v 0$, and is subjected to a constant force of $f$ at an angle of $ theta$ to the direction of velocity. An object with a mass of $m$ falls freely from a height along an arc road with a radius of $r$ and an angle of $ alpha$ to the vertical direction, and the velocity of the object at the moment of leaving the road.

Thermal Problem: An ideal gas undergoes an adiabatic process with an initial state of $(p 1,v 1)$ and an end state of $(p 2,v 2)$, and the temperature change of the gas in this process is found. An object with a mass of $m$ collides with a solid with a velocity of $v 0$ and a temperature of $m$ and a temperature of $t$.

Suppose the collision is a fully elastic collision with a heat capacity of $c$ and a heat withering or conductivity of $k$, ignoring the change in the volume of the ridged solid.

What to choose for this question, please answer it.

Question 7. Hurry up, okay. Is it so difficult, this question.

I think it's good to choose B, hello <>

The answer you're looking for: Choose D for the answer to this question

Summary. 1 Impulse (1) Definition: The product of the force and the time of action of the force (2) Formula:

i ft, which is suitable for finding the impulse of a constant force (3) direction: the same direction as force f 2 momentum (1) definition: the product of the mass of an object and its velocity (2) Formula:

p＝mv.(3) Unit: kilograms, meters, seconds, symbol:

kg·m/s.(4) Significance: Momentum is a physical quantity that describes the state of motion of an object, and it is a vector quantity, and its direction is the same as the direction of velocity

Hello! Send the question, you can take a picture and send it.

How do you use the momentum theorem column?

And I don't understand what the impulse is.

You first understand the momentum theorem (1) Content: The impulse of the net force on the object is equal to the increment of the momentum of the object (2) Expression: f·δt δp p p

3) Vector: The direction of momentum change is the same as that of the resultant land crack, and the momentum theorem can be used in a certain direction

I guess it's not the support of the earth.

The f here is the resultant force.

So the support force is subtracted by gravity, but the support force is varied, so it is multiplied by time.

And the support force is the impulse?

1 Impulse (1) Definition: Product of Force and Force Action Time (2) Formula: i ft, applicable to finding the impulse of a constant force (3) Direction:

The same direction as the force f 2 volt momentum Huizhou impulse (1) Definition: the product of the mass and velocity of the object (2) Formula: p mv

3) Unit: kilograms·meters and seconds, symbol: kg·m s.

4) Significance: Momentum is a physical quantity that describes the state of motion of an object, and it is a vector quantity, and its direction is the same as that of velocity

Impulse is not a supporting force, there are two forces here, one gravity and one support, both can be used as impulses, but in the end people are a whole problem.

Overall. So, at this time, it should be the resultant force of gravity and the supporting force as the impulsive force.

So at the end of the day, when the support force is equal to the gravitational force, is the support force still the impulse force in the book? If so, is the end of the twig impulse equal to gravity? So the impulse is to change from zero to big and then small, and finally equal to Chongzhou search force?

The impulse should change from large to small.

Because the athlete is falling, there is no buffer time when touching the mat.

This time is getting smaller.

Later, it became 0

1. The boiling water continues to absorb heat, and the temperature remains the same, which is emphasized in the question after a period of time, so the heat absorbed by the three balls is the temperature of the boiling water, that is, the same temperature is raised.

2. Consuming the same quality of alcohol, the same amount of heat is released, so water and oil absorb the same heat, and water and oil have different heat-absorbing capabilities, so they raise different temperatures.

Because the boiling water is only 100 degrees Celsius, and it has been left for a long time, although the iron balls, aluminum balls and copper balls are heated to 100 degrees for different times, but the time is enough for them to heat up to 100 degrees.

The temperature of the second fire is very high, and the oil and water do not reach the boiling point, the temperature is still rising, so the temperature is different.

Boiling water temperature 100

The temperature has been 100 for a while.

The temperature is the same, and the specific heat capacity is different, and the heat absorption is different.