P5 - Gravity and Orbits Flashcards
What happens if an object is travelling in a circle?
- If an object is travelling in a circle, it is constantly changing direction.
- This means there must be a force acting on it.
What is an orbit?
- An orbit is a balance between the forward motion of the object and a force pulling it inwards.
- This is called a centripetal force - it is directed towards the centre of the circle.
Why does the Moon orbit the Earth?
Moon orbits the Earth because of the centripetal force produced by the gravitational force between each planet and the sun.
Why do planets orbit the sun?
- The planets move around the sun in almost circular orbits.
* The centripetal forces that make this happen are provided by the gravitational force between each planet.
Why do artificial satellites orbit the Earth?
- The centripetal force is provided by the Earth, and they have a strong pull into the Earth’s orbit.
- They keep accelerating towards the Earth, but their tangential motion ( at a right angle to the acceleration ) keeps them in an almost circular orbit.
What is the correlation between mass and gravitational force size?
• The greater the mass, the greater the gravitational force, and the farther it can travel.
What is the correlation between distance & gravitational pull?
• The closer you get to a planet/star the greater the gravitational pull.
What force holds Moons, artificial satellites and space stations in orbit?
• Gravity
What orbit do periodic comets have?
- Periodic comets orbit the sun.
* They have a highly elliptical ( elongated ) orbit.
How do comets change speed?
- Periodic comets orbit the sun with an elliptical orbit.
- The orbits take them a long way from the sun, then back close again.• The closer the comet is to the sun the greater the gravitational force of attraction
- Comets travels much faster nearer to the sun, than it does in more distant parts of the orbit.
