High School Physics Navigation Three Cosmic Speeds, High School Physics How to Understand the Three

1. The launch speed is the speed at which the satellite and the launch vehicle are separated. 2. If the launch speed is lower than the first cosmic velocity, the launched satellite will return to the ground due to the gravitational pull of the earth, so the first cosmic velocity is the minimum launch velocity. So, you're right to understand it that way

According to the law of conservation of energy, the higher the height of the object, the greater the potential energy and the smaller the kinetic energy. That is, when the satellite is not affected by forces other than the earth's gravity, the farther away from the ground the speed is, the smaller the speed, so the first cosmic velocity is the maximum orbital velocity. [Your understanding is also correct].

When the spacecraft exceeds the first cosmic velocity and reaches a certain value, it will break away from the earth's gravitational field and become an artificial planet orbiting the sun, which is called the second cosmic velocity (11 2 kilometers per second), also known as escape velocity. [This is when the speed is greater, it will escape, and at that time it will not be called a satellite but a planet].

When the velocity is not equal to the first cosmic velocity, the spacecraft moves along an elliptical orbit around the center of the earth, and when the velocity is less than the first cosmic velocity, it does not fail to launch, but turns around and returns without leaving the atmosphere and finally hits the ground, when the velocity exceeds the first cosmic velocity and does not reach the second cosmic velocity, the spacecraft still moves around the center of the earth, but an elliptical trajectory with the center of the earth as a focus, and when the velocity exceeds the second cosmic velocity, the spacecraft changes to move along a hyperbola with the center of the earth as the focus, and will not come back.

I understand it this way: the force provided by the earth at a certain location is constant, and the velocity is too small, so that the centripetal force required for circular motion is less than the gravitational force provided by the earth, and there is a near-centric motion, so it cannot be launched.

v = root number (gm r ) The smaller the velocity, the larger the radius.

The first problem is not that it cannot be launched, but that it cannot be detoured. The second question is that you must know one is the speed of the detour and the other is the speed of the launch. The greater the circumnavigation speed, the closer it is to the center of the earth, and of course it is on the premise that it can go around.

The greater the launch speed, the farther it will naturally be from the Earth, and of course he has prerequisites.

First cosmic velocity = 7 9 km/s; Second cosmic velocity = 11 2 km/s; Third, cosmic velocity = 16 7 km/s.

First, the definition and elaboration of the velocity of the universe.

First cosmic velocity: Breaking away from the Earth's gravity and orbiting the Earth.

Second cosmic velocity: out of the Earth's orbit and around the Sun.

Third cosmic velocity: Break away from the sun and fly into outer space.

The premise of these three velocities is to start from the earth, in order to achieve different results to calculate the velocity, all the need for this speed is because of the existence of gravity, in the earth can also be understood as gravity, for example, you want to throw a stone into the universe, is it possible? It's impossible, because your speed is not enough, after it rises to a certain height, it will be "pulled" back to the earth due to the gravity of the earth, so if you don't want to be "pulled" back, you have to reach the first cosmic velocity; The same is true for understanding the second and third cosmic velocities.

Upstairs is at fault. Don't mislead people.

The speed of the universe seems simple, but I believe that many physics teachers have not figured it out, and the simple definition in the book is also embarrassing, and it took me a long time to really figure it out

The first cosmic velocity: the minimum launch velocity of an object that wants to leave the earth's surface, including flying around the earth Note that cosmic velocity refers to the launch speed rather than the operating speed, because the near-Earth satellite is close to the earth, so the gravitational force received by the earth is the largest, so the near-earth satellite to provide centripetal force is the largest, which means that the speed is the fastest kilometer per second, the higher the orbit, the smaller the speed.

The velocity is between the first and second cosmic velocities: the orbit of the satellite can only be elliptical, because when the satellite is at perigee, the velocity is greater than the first cosmic velocity, and the centripetal force is greater than the gravitational force, at this time the satellite is far away from the earth, and the velocity is constantly decreasing The process of converting kinetic energy into gravitational potential energy is apogee, and when it decreases to the point where gravity is greater than centripetal force, it is apogee, and the satellite flies to the earth again under the action of gravity, at which point the gravitational potential energy is converted into kinetic energy. Since there is no drag in space, the satellite orbits the Earth in an elliptical orbit.

The closer the maximum velocity is to the second cosmic velocity, the elliptical orbit is flattened, and the closer to the first cosmic velocity the orbit becomes.

If you still don't understand, you can continue to ask questions, and I can help you answer your questions.

I understand it this way.

The force provided by the earth at a certain location is constant.

If the velocity is too small, the centripetal force required for circular motion is less than the gravitational force provided by the earth, and the near-centric motion cannot be emitted.

v = root number (gm r).

It can be seen that the speed is smaller.

The larger the radius.

The first cosmic velocity is the velocity around the earth! i.e. according to mg=mv2r.

r is the radius of the earth.

The second cosmic velocity is the detachment velocity, which is a uniform circular motion around the sun.

Third cosmic velocity: also known as escape velocity.

The first cosmic velocity is the velocity around the earth! That is, according to mg=mv 2 r, r is the radius of the earth, and the second cosmic velocity is the detachment velocity, that is, it moves in a uniform circular motion around the sun.

According to mg=gmm, R2, gr, 2=gm (**substitution), and then according to t=2, the root number R, 3 gm.

t=2 root number (r+h) 3 gm = 24 hours The rest of the calculation process is not written, but it is roughly calculated to be about 36000km

According to v=root, gm (r+h), it can be roughly calculated that the approximate value is fixed and will not change.

Note: r refers to the orbital radius and r refers to the radius of the earth.

According to the formula of gravitational force f=g*mm r*r, (explain that f is the gravitational force of the object, g is a constant and you can leave it alone, m is the mass of the celestial body (in this case the moon and the earth), r is the distance between the object and the celestial body (in this case the diameter of the earth or the moon)).

Analysis: If the gravitational pull of the Moon is 1 6 of the Earth, then the gravitational acceleration is about 1 6 (m is constant according to g = mg).Therefore, choosing D, for A, only R is taken into account and not the mass of the Moon, M, it is obvious that conclusions cannot be drawn from this aspect alone; For b, only the mass of the moon m is considered and not the r in the formula is also wrong; For c with"The Moon attracts the Earth"with"The Earth attracts the Moon"It doesn't matter at all, but it should be"The moon attracts objects"with"The Earth attracts objects"and therefore also wrong; Only what is said in D"The gravitational force of an object on the surface of the Moon"It is the f in the formula, and it can be seen that f contains both m and r aspects, which is completely correct.

mg=gmm/r^2

gm=gr^2

So: f=gmm (r+h) 2=gr 2*m (r+h) 2 or: f=m(r+h) 2* 2

So there are two expressions asked.

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Near-Earth satellites are satellites with the smallest period, and the orbital radius is replaced by the Earth's radius, and then the formula GM r 2=(2pie t0 2)r is used

Calculate the city in 84 minutes.

v v=gr (v is the first cosmic velocity, g is the gravitational acceleration of the planet's surface, r is the radius of the planet) Please refer to the second volume of high school physics for details (pay attention to the unified unit when calculating!). ）

The first cosmic velocity refers to the velocity when the object orbits around the surface of the planet (it must fly close to the ground, because when the altitude increases, the speed of the object in a standard circular orbit is always lower than the first cosmic velocity) and the planet has no supporting force at all for the object, in other words, the gravitational force provides the centripetal force completely.

First, the definition and elaboration of the velocity of the universe.

As a result, it was.

Calculation: Calculated with the formula of gravitation and the formula of centripetal force: gmm r 2 = mv 2 r

This gives (gm r), which is the first velocity of the universe sought.

where g is the gravitational constant, m is the mass of the earth, and r is the radius of the earth. The satellite moves on the earth's surface, so gmm r 2 = mg, which can be replaced by ** as follows: gm = gr 2, from which v = (gr) , where g is the acceleration of gravity on the earth's surface and r is the radius of the earth.

v v=gr (v is the first cosmic velocity, g is the gravitational acceleration of the planet's surface, r is the radius of the planet) Please refer to the second volume of high school physics for details (pay attention to the unified unit when calculating!). ）

The first cosmic velocity refers to the velocity when the object orbits around the surface of the planet (it must fly close to the ground, because when the altitude increases, the speed of the object in a standard circular orbit is always lower than the first cosmic velocity) and the planet has no supporting force at all for the object, in other words, the gravitational force provides the centripetal force completely.