Gravity and satellites
This Topic is About...
- I will learn about gravity.
- I will use a model to see how gravity keeps a satellite in orbit.
- I will learn that a satellite is an object in space that orbits a larger object.
- I will learn to draw a force diagram to show forces acting on an object.
Let’s explore the wonders of gravity!
Key Words
- artificial satellite
- gravity
- orbit
- satellite
- force diagram
Tap to Learn the Meanings!
- artificial satellite: A man-made object placed in space to orbit a planet or moon.
- gravity: The force that pulls objects toward the ground.
- orbit: The path an object follows as it moves around another object in space.
- satellite: A natural or artificial object that orbits a planet or star.
- force diagram: A drawing that shows the direction and size of forces acting on an object.
Great job learning new science words!
How much gravity?
HAll objects exert gravity. When there are two objects, they exert gravity on each other. The amount of gravity an object has depends on size. The larger the object, the greater the force of gravity. Gravity works over a distance. So the amount of gravity also depends on how close the objects are: the closer the objects are, the stronger the forces of gravity between them. We are going to look at satellites as an example of this.
Satellites
SIn space, a body which orbits a larger body is called a satellite. The moon is a natural satellite of the Earth.
The moon and the Earth are attracted towards each other by gravity. The Earth is larger than the moon. So the Earth exerts a greater force of gravity on the moon than the moon exerts on the Earth. Look at this model of the moon orbiting the Earth.
Key points
TThe force of gravity is weaker the further the objects are apart.
Orbiting around the Earth
PPoint to the Earth. Point to the moon. Point to the moon's orbit around the Earth.
Find the green arrow. The green arrow shows the force of gravity the moon exerts on the Earth. Remember gravity is a pulling force so the moon is pulling the Earth. That is why the arrow points towards the moon.
Find the red arrow. The red arrow shows the force of gravity the Earth exerts on the moon.
Think like a scientist 2
Question: How does gravity keep the moon in orbit around the Earth?
Steps:
- Which is greater, the pull of gravity that the moon exerts on the Earth or the pull of gravity that the Earth exerts on the moon?
- How does the diagram on the previous page show this?
- Explain why one force of gravity is greater than the other.
- What path would the moon take if there was no gravity?
- List ways that the diagram is a good model to explain how the moon orbits the Earth.
How am I doing?
Answer ‘very well’, ‘better than before’ or ‘I still need more practice’ to these questions:
- How well can I identify forces on a force diagram?
- How well can I draw a force diagram?
Safety Tips:
- Always follow safety guidelines when working with experiments involving force or motion.
- Ensure you're using equipment properly and safely when drawing force diagrams.
Artificial Satellites 🛰️
Scientists have used what they know about natural satellites to design and make satellites. These satellites are called artificial satellites. There are many artificial satellites which orbit the Earth. Artificial satellites have a positive effect on our lives and environment. For example, some of the satellites continuously take photographs which help to make weather predictions. Other satellites provide TV signals and GPS used on ships, aeroplanes and some cars.
The International Space Station 🧑🚀
The International Space Station is an artificial satellite that has scientists living on it for years at a time. The scientists carry out investigations in space and use their findings back on Earth.
How Does an Artificial Satellite Get into Space? 🚀
An artificial satellite is launched into space by powerful rockets. The satellite travels at an enormous speed to overcome the pull of gravity that tries to bring it back toward Earth. When it reaches a certain distance above the planet, it continues moving at the same speed in a path around Earth. Gravity keeps pulling the satellite toward the centre of the Earth, and this constant pull keeps it in orbit instead of letting it fly off into space.
