In studying gravitation, Newton concluded that the gravitational attractive force that exists between any two masses: Candidates often lose marks for using 10ms –2 when the formula sheet gives g = 9.81ms –2 Gravitational field strength is a vector quantity: its direction is towards the object that causes the field.Īlways use the given value for g. If the gravitational field strength at any point is known, then the size of the force can be calculated. The less concentrated the field lines, the smaller the force. The force exerted on an object in a gravitational field depends on its position. The Earth’s gravitational field is radial the field lines become less concentrated with increasing distance from the Earth. The Earth’s gravitational pull acts towards the centre of the Earth Gravitational forces are always attractive – the Earth cannot repel any objects The lines show the direction of the force that acts on a mass that is within the field. The diagram represents the Earth’s gravitational field. This explains why we are aware of the force that attracts us and other objects towards the Earth – the Earth is very massive. Gravitational attractive forces between two objects only affect their motion when at least one of the objects is very massive. The attractive force between them is tiny, and very much smaller than the frictional forces that oppose their motion. This seems surprising, since any two objects placed close together on a desktop do not immediately move together. Newton realised that all objects with mass attract each other. Radiant energy such as light has mass and so is affected by gravitational fields. There are key definitions and concepts that are common to all three types of field. These three types of field have many similar properties and some important differences. magnetic fields affect permanent magnets and electric currents.electric fields affect anything that has charge.gravitational fields affect anything that has mass.In this and subsequent sections three types of field are considered: The following sections can be found belowĪ field is a region of space where forces are exerted on objects with certain properties. Recall and use the relationship that describes the gravitational force between two massesĭescribe the Earth’s gravitational field and explain how the field strength varies with distance from the centre of the Earth After studying this section you should be able to:
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