![]() This idea is also developed in the focus ideas It is helpful if students understand that the Earth and other planets orbit the sun, and that when things change direction (as the planets are constantly doing) they have a force on them. The gravity force on an object from the Earth is the same regardless of whether the object is surrounded by air (or water or anything else). The size of the gravity force at an altitude of 200km is still about 94% of what it was at sea level.) (An object needs to go much higher than a jumbo jet for major differences to occur. In everyday situations, the size of the gravity force on something does not change significantly as it rises above the Earth. A gravity force acts on an object regardless of whether it is moving or not moving. ![]() Students need opportunities for discussion that draws out the idea that gravity forces on objects are exerted by the whole Earth towards its centre. It is useful to focus separately on two areas where gravity is important: 1. The weight force on an object tells us the size of the gravity force from Earth acting on the object.Įxplore the relationships between ideas about gravity in theĬoncept Development Map - (Gravity, Stars).Because the Earth is so big, you have to travel to a very great height above the Earth’s surface before there are any detectable changes in the gravitational pull of the Earth (there is only about 0.25% reduction at the top of Mt Everest).The gravitational force is extremely hard to detect unless at least one of the objects has a lot of mass.The gravitational force weakens rapidly with increasing distance between masses.The greater the size of the masses, the greater the size of the gravitational force (also called the gravity force).Gravitational force is an attraction between masses.In all attempts to compare gravitational forces with other forces, they are relatively much weaker than We only notice gravitational forces if one of the objects involved has a huge mass (such as the Earth). The vast difference in mass between the Earth and the falling object means the Earth’s movement is imperceptibly small. Both objects exert an equal attractive force on each other: a falling object is attracting the Earth with the same size force as the Earth is attracting it. The size of the gravitational force is proportional to the masses of the objects and weakens as the distance between them increases. There is a gravitational force of attraction between every object in the universe. Gravitational forces are considered to be inherently linked to what we call ‘ mass’. there is no gravity in a spacecraft orbiting the Earth.gravity acts upwards on things that are moving upwards.It does not operate on things that are moving upwards gravity affects things while they are falling but stops when they reach the ground.gravity is caused by the Earth spinning.gravity is significantly less on high mountains or tall buildings and increases as we lose height (which is why falling objects speed up).(Hence there is no gravity on the moon, in Earth satellites or in space as one rises above the surface of the Earth gravity lessens because the atmosphere thins) gravity is related to the presence of air, or is something in the air, so if there is no air, there is no gravity.gravity is a push from above (in some instances due to air pressure).Students may have a range of views about gravity: This idea is also developed in the focus idea Students’ views about gravity, the shape of the Earth, and the direction of ‘down’ are often intertwined. Things falling towards the Earth are such familiar occurrences that students may consider these events as ‘natural’ with no need for further explanation.Įven students who use the word ‘gravity’ in an appropriate context may not be able to be able to explain what it is, or will be inconsistent in their explanations. Contrasting student and scientific viewsĬontrasting student and scientific views Student everyday experiences.
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