Why does a satellite in a circular orbit travel at a constant speed? There is no component of force acting along the direction of motion of the satellite. The net force acting on the satellite is zero. The gravitational force acting on the satellite is balanced by the centrifugal force acting on the satellite.

## Does a satellite in a circular orbit travel at a constant speed?

Its speed does not change , but its velocity (speed and direction) does. Acceleration (as in F=ma ) implies a change of velocity but not necessarily of speed. A circular orbit is the orbit which is exactly balanced so that the speed never changes.

#### Why does a satellite moves in a circular orbit?

But the gravitational force always try to pull the satellite towards itself , so the satellite continuously changes its direction without changing its speed so as to revolve in a circular orbit and centripetal force can balance the gravitational force.

### Why does a satellite have constant speed but not constant velocity?

Example — Gravitational attraction provides the centripetal force needed to keep a planet in orbit around the Sun, and a satellite in orbit around a planet. For example, gravitational attraction between the Earth and the Moon keeps the Moon in orbit around the Earth. An object moving in a circular orbit at a constant speed has a changing velocity. This is because velocity is a vector quantity that depends on speed and direction.

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### Why can satellites travel at any speed in a particular orbit?

Why can’t satellites travel at any speed in a particular orbit? The horizontal speed must give a centripetal acceleration which is exactly equal to the gravitational acceleration. The orbit of each planet around the Sun is an ellipse with the Sun at one focus.

## Why does the speed of a satellite not change?

For simplicity, consider a perfectly circular orbit; the gravitational acceleration is always at a right angle to the velocity vector. This means that the speed cannot change despite the fact that there is constant acceleration. Note that for the speed to change, there must be a non-zero component of acceleration parallel (or anti-parallel) to the velocity vector.

## Why are satellites constantly accelerating?

Satellite Motion — A satellite is often thought of as being a projectile which is orbiting the Earth. But how can a projectile orbit the Earth? Doesn’t a projectile accelerate towards the Earth under the influence of gravity? And as such, wouldn’t any projectile ultimately fall towards the Earth and collide with the Earth, thus ceasing its orbit? These are all good questions and represent stumbling blocks for many students of physics. Indeed, a satellite is a projectile. Second, a satellite is acted upon by the force of gravity and this force does accelerate it towards the Earth. In the absence of gravity a satellite would move in a straight line path tangent to the Earth. In the absence of any forces whatsoever, an object in motion (such as a satellite) would continue in motion with the same speed and in the same direction.

- We will discuss each question here;
- First, an orbiting satellite is a projectile in the sense that the only force acting upon an orbiting satellite is the force of gravity;
- Most Earth-orbiting satellites are orbiting at a distance high above the Earth such that their motion is unaffected by forces of air resistance;

This is the law of inertia. The force of gravity acts upon a high speed satellite to deviate its trajectory from a straight-line inertial path. Indeed, a satellite is accelerating towards the Earth due to the force of gravity. Finally, a satellite does fall towards the Earth; only it never falls into the Earth.

- To understand this concept, we have to remind ourselves of the fact that the Earth is round; that is the Earth curves;
- In fact, scientists know that on average, the Earth curves approximately 5 meters downward for every 8000 meters along its horizon;

If you were to look out horizontally along the horizon of the Earth for 8000 meters, you would observe that the Earth curves downwards below this straight-line path a distance of 5 meters. In order for a satellite to successfully orbit the Earth, it must travel a horizontal distance of 8000 meters before falling a vertical distance of 5 meters.

- A horizontally launched projectile falls a vertical distance of 5 meters in its first second of motion;
- To avoid hitting the Earth, an orbiting projectile must be launched with a horizontal speed of 8000 m/s;

When launched at this speed, the projectile will fall towards the Earth with a trajectory which matches the curvature of the Earth. As such, the projectile will fall around the Earth, always accelerating towards it under the influence of gravity, yet never colliding into it since the Earth is constantly curving at the same rate. Such a projectile is an orbiting satellite. To further understanding the concept of a projectile orbiting around the Earth, consider the following thought experiment. Suppose that a very powerful cannon was mounted on top of a very tall mountain. Suppose that the mountain was so tall that any object set in motion from the mountaintop would be unaffected by air drag.

Suppose that several cannonballs were fired from the cannon at various speeds — say speeds of 8000 m/s, less than 8000 m/s, and more than 8000 m/s. A cannonball launched with speeds less than 8000 m/s would eventually fall to the Earth.

A cannonball launched with a speed of 8000 m/s would orbit the Earth in a circular path. Finally, a cannonball launched with a speed greater than 8000 m/s would orbit the Earth in an elliptical path. The animations below depict these ideas. Two final notes should be made about satellite motion.

First, the 8000 m/s figure used in the above discussion applies to satellites launched from heights just above Earth’s surface. Since gravitational influences decrease with the height above the Earth, the orbital speed required for a circular orbit is less than 8000 m/s at significantly greater heights above Earth’s surface.

Second, there is an upper limit on the orbital speed of a satellite. If launched with too great of a speed, a projectile will escape Earth’s gravitational influences and continue in motion without actually orbiting the Earth. Such a projectile will continue in motion until influenced by the gravitational influences of other celestial bodies.

### Which one is constant for a satellite in orbit?

According to Kepler, Angular momentum is conserved for a satellite in orbit.

### What force keeps a satellite in orbit?

So, How Do Satellites Stay in Orbit? — Satellites are able to orbit around the planet because they are locked into speeds that are fast enough to defeat the downward pull of gravity. Satellites are sent into space by a rocket launched from the ground with enough energy (at least 25,039 mph!) to get outside our atmosphere.

- Once the rocket reaches its determined location it drops the satellite into its orbit;
- The initial speed of the satellite maintained as it detaches from the launch vehicle is enough to keep a satellite on orbit for hundreds of years;

A satellite maintains its orbit by balancing two factors: its velocity (the speed it takes to travel in a straight line) and the gravitational pull that Earth has on it. A satellite orbiting closer to the Earth requires more velocity to resist the stronger gravitational pull.

#### Why a satellite moves around the earth in its orbit and does not escape from the space?

The Short Answer: Satellites don’t fall from the sky because they are orbiting Earth. Even when satellites are thousands of miles away, Earth’s gravity still tugs on them. Gravity—combined with the satellite’s momentum from its launch into space—cause the satellite to go into orbit above Earth, instead of falling back down to the ground. .

### When a satellite travels at constant speed What is the shape?

A satellite in orbit around Earth traces an oval-shaped path called an ellipse. An ellipse is the closed path taken by a point that moves in such a way that the sum of its distances from two fixed points is constant.

## What is true about circular orbit?

Circular orbits are the simplest kinds of orbits in celestial mechanics, where an orbiting body remains at constant radius as it travels around a gravitating mass.

## Do all satellites move at the same speed?

Do ALL satellites have to fly at the same speed so not to leave their orbit? — A: No, satellites that orbit at different altitudes have different speeds. Satellites that are further away actually travel slower. The International Space Station has a Low Earth Orbit, about 400 kilometers (250 miles) above the earth’s surface.

Objects orbiting at that altitude travel about 28,000 kilometers per hour (17,500 miles per hour). The GOES system of satellites, which tracks weather and other things, is in a geosynchronous orbit, 36,000 kilometers (22,000 miles) above the earth.

These satellites travel at about 11,000 kilometers per hour (7,000 miles per hour). The moon, at about 380,000 kilometers from the earth (240,000 miles) only travels about 3,700 kilometers per hour (2,300 miles per hour). Posted on January 17, 2013 at 5:42 pm Categories:.

### How do satellites maintain speed?

So, How Do Satellites Stay in Orbit? — Satellites are able to orbit around the planet because they are locked into speeds that are fast enough to defeat the downward pull of gravity. Satellites are sent into space by a rocket launched from the ground with enough energy (at least 25,039 mph!) to get outside our atmosphere.

- Once the rocket reaches its determined location it drops the satellite into its orbit;
- The initial speed of the satellite maintained as it detaches from the launch vehicle is enough to keep a satellite on orbit for hundreds of years;

A satellite maintains its orbit by balancing two factors: its velocity (the speed it takes to travel in a straight line) and the gravitational pull that Earth has on it. A satellite orbiting closer to the Earth requires more velocity to resist the stronger gravitational pull.

#### What is true about circular orbit?

Circular orbits are the simplest kinds of orbits in celestial mechanics, where an orbiting body remains at constant radius as it travels around a gravitating mass.

## Does a satellite have a constant vertical acceleration?

Circular Motion Forces and Motion Teaching Guidance for 14-16 This sequence of ideas can help students understand orbital motion. Throw a ball out horizontally. It falls to the ground some distance away. A rifle bullet, fired faster but also horizontally, reaches the ground after a kilometre or so. A thought experiment: fire a bullet so fast that it covers an appreciable part of the Earth’s circumference before it reaches the ground. To the bullet, all parts of the Earth are the same. It soon forgets where it started from. With just the right speed, it will always be falling over the edge and so it will go on round the Earth (keeping just above the ground) until it arrives back at the starting point and hits us from behind. The bullet started off as a projectile with a constant horizontal velocity and a vertical acceleration due to gravity.

- What effect does the Earth’s curvature have on the bullet’s fate? Fire it even faster and it ‘falls over the edge of the Earth’;
- The Earth falls away from the bullet’s original direction at exactly the same rate as the bullet falls;

Therefore at every point in its orbit the Earth satellite must have a constant acceleration towards the centre of the Earth. Newton imagined that if he threw the stone fast enough it would orbit the Earth because it is always falling towards the Earth at the same rate as the Earth «falls away» from it. This thought experiment is sometimes known as Newton’s cannon and is available as a computer simulation or video. In practice air resistance absorbs energy and down comes the bullet, so you must start outside the atmosphere. When a rocket is used to launch a satellite, the motions of rocket and satellite can be analyzed like this:

- The rocket starts off nearly vertically. The exhaust gases exert an upward push greater than the rocket’s weight, so that the rocket accelerates upwards.
- Fuel exhausted; motor cuts out; first stage jettisoned.
- Parabolic (free-fall trajectory until the path is horizontal at maximum altitude.

Final stage ignites and accelerates its relatively small mass to high velocity. Satellite unlatched and left in orbit. Final stage is also in orbit but at a slower speed so it gets left behind..

### Is satellite accelerated motion?

The rate of change of velocity with respect to time is called acceleration. Therefore, the motion of the satellite around the earth is an accelerated motion.